Sox, JVo.
Essex Institute.
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its veceiiJt.
ELEMENTS
OF
SCIENCE AND ART.
VOL. II.
London :
Printed by A, & R. Spottiswoode,
New-Street-Square.
ELEMENTS
SCIENCE AND ART:
FAMILIAR INTRODUCTION
NATURAL PHILOSOPHY AND CHEMISTRY:
TOGETHER WITH
THEIR APPLICATION TO A VARIETY OF ELEGANT
AND USEFUL ARTS.
By JOHN IMISON.
A NEW EDITION,
Considerably enlarged, and adapted to the improved State of Science,
By THOMAS WEBSTER, Sec. G. S.
IN TWO VOLUMES.
VOL. II.
LONDON:
PRINTED FOR F. C. AND J. RIVINGTONJ J. SCATCHEBD ; J. NUNN;
LONGMAN, HURST, REES, ORME AND BROWNJ T. CADELL; S. BAGSTER;
J. booth; J. booker; j. Murray; j. richardson; Baldwin,
CRADOCK AND JOY; BAYNES AND SON; J.HARDING; SHERWOOD,
NEELY AND JONES ; G. AND w. B. whittaker; t. tegg; j.bobinson;
AND E. EDWARDS.
1822.
CONTENTS
THE SECOND VOLUME.
CHEMISTRY.
Page
Simple substances 3
Operations and instruments in chemistry 4*
Pneumato-chemical apparatus 12
Of the nomenclature of chemistry 19
Caloric 22
Light 33
Electricity 35
Oxygen -. 36
Nitrogen 39
Combinations of oxygen and nitrogen 40
Nitrous acid 44-
Nitric acid 45
Atmospheric air 46
Hydrogen 49
Hydrogen and oxygen 54
Hydrogen and carbon 59
Sulphuretted hydrogen gas 61
Phosphuretted hydrogen gas 62
Chlorine 63
Iodine 66
Sulphur 67
Sulphuric acid 69
Carbon 70
Carbon and oxygen 71
Carbon and nitroffen 74
Phosphorus .,, , ,,,,, 74
VI CONTENTS.
Page
Phosphorus and oxygen 76
Boron 76
Fluorine » 77
Alkahes 78
Potash 79
Soda , 82
Lithia 84
Ammonia 85
Earths 86
Lime 87
Magnesia 89
Barytes 89
Strontia 90
Silica 90
Alumina 91
Yttria 92
Glucma 93
Zirconia 93
Thorina..... 93
Metals i 94
Platina 98
Gold 99
Silver 101
Mercury 103
Iron 104-
Copper 109
Tin Ill
Lead Ill
Zinc 114
Antimony 115
Bismuth 116
Arsenic 117
Nickel 117
Manganese 118
Cobalt 119
Molybdena 120
Tmlgsten 120
Osmium 121
Iridium 121
Pihodium 121
CONTENTS. vii
Page
Panadium 122
Cadmium • 122
Tellurium 122
Titanium 123
Chromium 123
Uranium 124?
Columbium 124*
Cerium 124<
Selenium 125
Vegetable substances , 125
Animal substances 137
Nomenclature of chemistry 142
MANUFACTURES'AND ARTS.
Making bread 147
Brewing , 153
Bleaching 160
Dyeing 178
Callico printing 198
Tanning 101
Currying i..., 211
Manufacture of soda 212
Manufacture of potash 214
Refining metals , 215
Pottery 228
Manufacture of glass 235
Varnishing 239
Japanning 248
Lacquering 258
Gilding 261
Silvering • 275
Tinning 281
Bronzing 282
Soldering 283
Moulding and casting 284
Cements 292
Lutes 304
Ink making 306
Removing stains 310
vm CONTENTS.
Staining wood 313
Staining ivory 316
Miscellaneous receipts 317
FINE ARTS.
Drawing -... 342
Geometry 348
Perspective 374-
Drawing the figure 388
Drawing landscapes 400
Mechanical drawing 403
Painting transparencies 407
Crayon painting 409
Colours 410
Of engraving 419
Etching 423
Mezzotinta scraping , 431
Aqua tinta , 432
Wood cutting 442
Etching on glass 442
Lithography , 445
ELEMENTS OF SCIENCE.
CHEMISTRY.
JHLiTHERTO we have considered the action of
bodies on each other in masses, or what is called
their mechanical actions ; and for this purpose it
was not necessary to attend particularly to the
difference in the many species or kinds of matter,
which we distinguish more or less readily.
But if we present bodies of different kinds to
each other in proper circumstances, a certain action
takes place between the minute particles of one sort
of substance upon those of another sort, by which,
frequently, the individual or peculiar properties of
eacli disappear, and a new substance is formed.
The study of this action of the minute or ulti-
mate particles of different kinds of matter on each
other is called chemistry^ and the powers thus ex-
erted occasion chemical actions.
Independently of the enlargement of our views
of nature, and the pleasure and entertainment de-
rived from contemplating her operations, chemistry
j^is essentially useful in many of the arts upan
VOL. IT. B
'■2 CHEMISTRY.
wliicli tlie comforts, and even the very existence,
of civilized life, depend.
As exani])les, we may mention the arts of
dyeing, bleaching, tanning, potting, glass-making,
baking, brewing, distilling, working metals, &c. &c.
which owe their present state of perfection to the
science of chemistry In agriculture it is capable of
affording great assistance, by explaining the nature
of soils and manures; and in medicine its import-
ance is invaluable, many of the most efficacious re-
medies being entirely formed by chemical processes.
In short, there is scarcely any art or trade which
either does not altogether depend upon, or may be
benefited by this science.
I3y chemical means we are enabled to reduce
compound bodies to the constituent principles of
which they are composed, and this operation is
called analysis, or decomposition. When a substance
cannot by any means be resolved into others, it is
called a simple body j and it is now known that
all that vast variety of substances which we see is
composed of a few simple bodies, which hence are
called elementary substances.
Formerly, air, earth, Jire, and icater, were sup-
posed to be the elements of which all bodies were
formed ; but modern chemistry has shown that this
was an erroneous supposition. For the air, or at-
mosphere, is compounded of several distinct kinds
of aerial fluids or gases. Instead of one kind of
earth, it is now known that there are several kinds.
Water is no longer considered as an element, being,
in fact, formed of two substances very different, viz.
of oxygen and hydrogen. Fire is less understood,
and is still retained as an element under the name
of caloric.
From the improvements that are continually
CHEMISTRY.
s
making in the methods of analyzing bodies, or
separating them into their component principles
or elements, several other substances once supposed
to be simple are now found to be compounds : and,
as chemistry continues to advance, the list of simple
substances may be reduced ; our inability to de-
compose any body not proving it to be simple, but
only, perhaps, that our methods of examination are
still imperfect.
The substances which hitherto have resisted all
the known methods of analysis, and which, in the
present state oi' our knowledge, are considered as
the elements of all bodies with which we are ac-
quainted, are the following : —
Substances not metallic.
8. Iodine
9. Sulphur
10. Carbon
11. Phosphorus
12. Boron
13. Fluorine.
1. Light
2. Caloric
3. Electric fluid
4. Oxygen
5. Nitrogen
6. Hydrogen
7. Chlorine
Metallic substances.
14. Potassium
15. Sodium
16. Lithium
17. Calcium
18. Magnium
19. Barium
20. Strontium
21. Silicium
22. Aluminum
23. Yttrium
24. Glucinum
25. Zirconium
26. Thorinum
27. Platina
28. Gold
29. Silver
Sa Mercury
31. Iron
32. Copper
33. Tin
34. Lead
35. Zmc
36. Antimony
37. Bismuth
38. Arsenic
39. Nickel
40. Manganese
41. Cobalt
42. Molybdena
43. Tungsten
44. Osmium
45. Iridium
46. Rhodium
47. Palladium
48. Cadmium
49. Tellurium
50. Titanium
51. Chromium
52. Uranium
53. Columbium
54. Cerium
55. Selenium.
4. OPERATIONS AND INSTRUMENTS
The utmost degree of mechanical division which
we can effect in bodies, by pounding, grinding, and
similar processes, can only reduce them to frag-
ments so small that they can no longer be per-
ceived by the sight ; but we cannot thus arrive at
those ultimate atoms, molecules, or particles, of
which the various s])ecies of matter are sup})osed to
consist, and which arc, perhaps, incapable of
subdivision.
Besides the attraction of gravitation possessed
in common by all matter, these elementary sub-
stances possess peculiar attractions for each other,
whi-cli are called chemical attractmis. By these
attractions, or affinities, as they are called, they
combine together, and form com])oimd bodies.
OPERATIONS AND INSTRUMENTS USED IN
CHEMISTRY.
The great principle of all chemical operations
which enable us to decompose certain bodies, and
to compound others, is, that every substance has a
pecidiar affinity or attraction for other substances,
but that it has different degrees of attraction for
different substances. This is called elective affinity
or attraction.
If some oil and some alkali be put together, they
will unite and form soap. But if to this a little
dilute sulphuric acid be added, the oil and alkali
will be separated from each other again ; the alkali
having a stronger attraction for the acid than it has
for the oil, will leave the latter and join the acid.
Dissolve some magnesia in nitric acid, and the
solution will be transparent. Also dissolve some
lime in water by letting it remain for some
hours: the solution of lime in water will also
USED IN CHEMISTRY. O
be transparent. Pour them together, and imme-
diately a turbid appearance will be presented, and
a white powder will fall to the bottom. This
powder will be found to be magnesia. The ex-
planation is this : the nitric acid has a greater
attraction for lime than it has for magnesia ; there-
fore, it lets fall the latter and takes up the former.
The substance thus thrown down is called a pre-
cipitate, and the process \'&c?i\\Qd. precipitation.
If all the bodies presented to each other are
compounds, sometimes two new substances are
formed. Thus, if solutions of nitrate of barytes
and of sulphate of soda be mixed together, the
former being composed of nitric acid and barytes,
and the latter of sulphuric acid and soda, two
new products will be obtained, viz. nitrate ot
soda and sulphate of barytes. For the nitric
acid will leave the barytes and join to tiie soda,
and the sulphuric acid will give up the soda and
seize the barytes. Tliis is called double elective
affinity, as the former example was of single
elective nffi^iity. When diiferent substances unite
chemically, and form a compound, they always unite
in the same proportion. Thus, water, which is
composed of oxygen and hydrogen, always con-
tains the same proportion of each ; that is, we do
not find that in several specimens of water the pro-
portions of oxygen and hydrogen vary. Also, if
an acid and an alkali combine together, and
thus form a certain salt, they always unite in the
same proportion to form that salt ; however, they
will sometimes combine in another proportion to
form another salt j but when substances unite in
more than one proportion, the second, third, &c.
proportions are multiples or divisors of the first.
This is one of the latest discoveries in chemistry,
B O
b OPERj^TlONS AND INSTRUMENTS
and has given rise to the doctrine of definite
proportions.
Here it must be remarked that chemical com-
bination and mechanical mixture are very different ;
since, although bodies only combine in definite
proportions, yet, they can be mixed together in all
proportions.
in general, before substances can be made to
act cliemically on each other, one of them, at
least, must be in a fluid state ; and, that solids
may be acted on more easily, they are generally
mechanically divided into small pieces, or reduced
to a powder.
By trituration^ pulverization, and levigation, is
meant the reduction of solids into pov^ders of dif-
ferent degrees of fineness. Brittle substances are
reduced to powder by means of hammers, pestles
and mortars, stones and mullers. Mortars and
pestles are made either of metal, glass, porcelain,
marble, agate, &c. according to the hardness and
properties of the bodies to be pounded. Wedge-
wood's ware affords a most excellent kind of mor-
tar for most purposes, as it is very strong, and not
liable to be acted upon by acids. Many bodies
cannot be reduced to powder by the foregoing
methods : such are fibrous substances, as wood,
horns of animals, elastic gum, and mettles which
flatten under tlie hammer ; for these, JileSy rasps,
knives y and graters, are necessary.
The separation of the finer parts of bodies from
the coarser which may want farther pulverization,
is performed by means of sifting or "djashing.
A sieve for sifting generally consists of a cylin-
drical band of thin wood, or metal, having silk,
leather, hair, wire, &c. stretched across it. They
are of diflerent degrees of fineness.
USED IN CHEMISTRY. 7
Washing is used for procuring powders of an
uniform fineness, much more accurately than by
means of the sieve ; but it can only be used for
such substances as are not acted upon by the fluid
which is used. The powdered substance is mixed
■with water, or other convenient fluid : the liquor
is allowed to settle for a few moments, and is then
decanted off; the coarsest powder remains at the
bottom of the vessel, and the finer passes over
with the liquor. By repeated decantations in this
manner, various sediments are obtained, of different
degrees of fineness : the last, or that which re-
mains longest suspended in the liquor, being the
finest.
Filtration is a finer species of sifting. It is
sifting through the pores of paper, or flannel, or
fine linen or sand, or pounded glass, or porous
stones, and the like ; but it is used only for separ-
ating fluids from solids, or gross particles that
may happen to be suspended in them, and not chcr
mically combined with the fluids. Thus salt water
cannot be deprived of its salt by filtration j but
muddy water will deposit its mud. No solid, even
in the form of powder, will pass through the above-
mentioned filtering substances : hence if water or
other fluid, containing sand, insects, mud, &c. be
placed in a bag or hollow vessel made of any of
those substances, the sand, &c. will remain upon the
filter, and the liquor will pass through, and may be
received clear in a vessel under it. Unsized paper
is a very convenient substance for making filters
for chemical purposes. It is wrapped up in a
conical form, and put into a glass funnel, which
serves to strengthen the paper and support the
weight of the fluid when poured into it.
Decantatioti.iS often substituted, instead of fil-
B 4
8 OPERATIONS AND INSTRUMENTS
tration, for separating solid particles which are
diffused through liquors. These are allowed to
settle to the bottom, and the clear fluid is gently
poured off. If the sediment be extremely light,
and apt to mix again with the fluid, by the slightest
motion, a syphon is used for drawing off the clear
fluid.
Limviation is the separation by means of water,
or other fluid, of such substances as are soluble in
it, from other substances that are not soluble in it.
Thus, if a certain mineral consists of salt and sand,
or salt and clay, &c. the given body being broken
to powder, is placed in water, which will dissolve
the salt, and keep it suspended, whilst the earthy
matter falls to the bottom of the vessel, and,
by means of filtration, may be separated from the
fluid.
Evaporation separates a fluid from a solid, or
a more volatile fluid from another which is less
volatile.
Simple evaporation is used when the more vola-
tile or fluid substance is not to be preserved.
Various degrees of heat are employed for this pur-
pose, according to the nature of the substances,
it is performed in vessels of wood, glass, metal,
porcelain, &c. Basons made of Wedcewood*s
ware are very convenient, as they are not apt to
break by sudden changes of heat. Small flasks of
thin glass also : these are placed either over the
naked fire, or in a vessel filled with sand, which is
then called a sand-bath. This affords a more re-
gular degree of heat, and renders the vessels less
liable to be broken.
When the fluid which is evaporated must be pre-
served, then the operation is called distillation.
Distillation is evaporating in close vessels, when
USED IN CHEMISTRY. 9
we wish to separate two fluids of different degrees
of volatility, and to preserve the most volatile, or
both of them. The substance to be subjected to
distillation is put into some vessel that will resist
the action of heat, called a retort, an alembic, or a
stilly having a beak or neck projecting from it, to
which is attached another vessel, to receive the
fluid that rises flrst, which is called the recipient,
or receiver. The vessel that contains the liquor to
be distilled is placed upon the fire, or in a sand-
bath, or over a lamp : the heat causes the most
volatile fluid to rise in the form of vapour, and to
pass into the receiver, where it is again condensed
by cold. This condensation is sometimes as-
sisted by making the vapour pass through a tube
which is immersed in a vessel containing cold
water.
A (Plate 1. fig. 1.), represents a retort used for
distillation. It is a vessel, either of glass or baked
earth, for containing the liquid to be distilled.
When it has a small neck, a, with a stopple fitted
to it, for introducing the materials through, it is
called a tubulated retort. B is the receiver for con-
densing the vapour which is raised, and into which
the neck of the retort is inserted. The joining, b,
is made air-tight by means of some substance ap-
plied to it, called a lute. Various methods are
used for supporting both the retort and receiver,
according to the degree of heat employed in the
process, and several other circumstances.
When great heat is employed, earthen retorts
are used, which are placed on or in the fire. When
a less heat is wanted, glass retorts are generally
employed, which must not not be placed imme-
diately on the fire, unless they are coated over
with a composition of clay and sand, which is
10 OPERATIONS AND INSTRUMENTS
sometimes done. Glass retorts are generally
placed in a sand-bath, or suspended over a lamp,
for which Argand's lamp is the best. The re-
ceiver is placed upon some stand convenient for
the purpose, with a ring made of hay under it, or
some such contrivance, to keep it steady.
A (Fig. 2.), is a vessel called a mattrass, for the
same purpose, having a vessel, B, called an alembic,
fitted to the head. The liquid raised by heat into
the state of vapour, is condensed in the alembic,
and falls into a groove all round its inside, from
whence it runs out by the spout, C, into the re-
ceiver, D.
Fig. 3. are conical tubes that fit into another,
for lengthening the necks of retorts, &c. to con-
nect them with the receivers at any distance: they
are called adopters.
Fig. 4. are phials with bent glass tubes fitted in
them, for disengaging gases, and similar experi-
ments : they were used by Priestley, and are
hence called Priestleij^s bottles, and sometimes
proofs : they are either tubulated or plain.
A (Fig. 5.), represents a common still. It is a
large vessel of copper, into which the materials
to be distilled are put. The still is built up in
brick-work, which covers it up to the neck; the
fire is applied underneath, and runs round it in a
spiral manner. B is the Jiead of the still. This
head is connected with the ivorm, which is a spiral
tube, immersed in a vessel of cold water, called the
refrigeratory, or cooling tube, C. The liquor be-
ing condensed in its passage through the worm,
runs out at the cock, D, into the vessel placed
there to receive it.
This is the construction of the common still for
distilling spirituous liquors ; but a very great im-
USED IN CHEMISTRY. 11
provement has been made upon this instrument, in
Scotland, within these few years. This improved
apparatus is known by the name of the Scotch
still, a section of which is represented, Fig. 6. The
principle of the improvement consists in exposing
a great quantity of the surface of the fluid to the
action of the fire, and affording a more ready means
for the escape of the vapour or gas.
A, is the body of the still, made very shallow
and concave at the bottom, in order that the fire
may act better upon it ; bb^ are a number of tubes
opening into the still, and communicating with the
neck of the still B, in order to convey the vapour
off as soon as it is formed ; cc, is a cover that shuts
down over the pipes and top of tlie still, to keep it
warm, by preventing the loss of heat which would
be occasioned by the contact of the cold air. This
is effected by the quantity of air that is confined
between the cover and tlie top of the still ; for it
is a fact which is now well known, that confined air
is a non-conductor of heat. In general, the heads
of stills are kept warm by laying blankets upon
them, at least when this is attended to, as it ought
always to be ; but this metallic covering, by sur-
rounding the still with a quantity of confined air,
answers the purpose still better.
When the materials which are evaporated con-
crete in a solid form, within the neck of the dis-
tilling vessels, then the distillation is more properly
called sublimation.
By the above means, one fluid may be separated
from other materials; but it often happens, that in
distillation the substances which are subjected to
this process have a chemical action upon each
other ; new combinations take place, and perma-
IS PNEUMAT0-CHE31ICAL APPARATUS.
nently elastic fluids or gases are disengaged, which
are required to be preserved and examined. For
tliis purpose, a very useful apparatus is employed,
called the
PNEUMATO-CHEMICAL APPARATUS.
Fig. 7, represents an improved pneumato-chemi-
cal apparatus and lamp-furnace connected with it.
A, is a vessel filled with water. In this vessel
a shelf is placed, so as to be a little under the
surface of the fluid, having several holes bored
through it, to which small funnels are attached
underneath.
The glass air-jar, or receiver, B, which is to re-
ceive and contain the gas, is filled with water, and
being inverted wdth its mouth under water, it is
raised up gently till its mouth is nearly out of the
water, but not quite ; and it is then placed upon
the shelf over one of the holes. The receiver will
remain full of water, w^iich is kept up by the
pressure of the atmosphere upon the principle of
the barometer described under pneumatics.
The materials from w^iich the gas is to be dis-
engaged, are now to be put into a glass retort, C,
which is put through, and suspended in one of the
rings of the lamp-furnace, D. An improved Ar-
gand's lamp, £, having teo co7icentric wic/cs,*
afl^brds a much greater degree of heat than the
common Argand's lamp, wdiich has only a single
circular Xiick; this is placed upon the shelf, F.
* This lamp with two concentric tvicks was first contrived by
the editor some years ago, and is extremely useful m some
chemical operations, as it gives a much greater heat than the
common Argand's lump with one circular wick.
PNEUMATO-CHEMICAL APPARATUS. 13
The shelf, with the lamp and the ring having the
retort in it, are now to be adjusted by moving them
up or down, until the lamp is at a convenient
height below the retort, the neck of whicli rests
upon the edge of the cistern, and the end of its
neck opens in the funnel under the jar standing
upon the shelf. The lamp must now be lighted,
and as soon as the substances in the retort act upon
each other sufficiently, the gas will begin to be dis-
engaged, and will ascend through the hole in the
shelf into the vessel, B, and displace the water witli
which it had been filled. When all the water is
displaced, the receiver is full of the gas which was
disengaged from the retort, and may be preserved
in it by keeping its mouth always under the water
in the cistern.
This gas may be transferred from the vessel, B,
into any other vessel, in the following manner : fill
the vessel into which the gas is to be transferred,
with the fluid in the trough, and place it on the
shelf as before directed, over one of the holes.
-Then take the vessel, B, and keeping its mouth still
under the fluid, bring it under the hole on which
.the vessel is placed, then depressing its bottom,
and elevating its mouth, so as to bring it more to a
horizontal position, the gas in it will escape and
rise up through the hole on which the other vessel
has been placed, and will fill it by displacing the
fluid. In this manner any gas may be formed, or
transferred from one vessel to another.
The cistern for the water may be made of wood,
in the manner of a tub, and hooped round, which
may or may not be painted inside and out. But it
will be much more elegant if made of sheet-iron,
tinned, and japanned of a brown or chocolate co-
lour. The ornaments, if any, may be of brass, or
14 PNEUMATO-CHEMICAL APPARATUS.
gilt. The best material for the lamp-furnace is
brass lackered, and the lamp should be of tin ja-
panned. The apparatus constructed in this man-
ner has an extremely elegant appearance, and is
found to answer perfectly well for a variety of che-
mical operations.
When the gas to be procured is absorbable by
water, quicksilver is used instead of water ; and,
as it is very expensive, a smaller vessel is neces-
sary, which must be made of some material not
acted upon by quicksilver, as wood or stone ; and
it must be sufficiently strong to resist the great
weight and pressure of the quicksilver. It is usually
cut out of a solid block of wood, or marble, or
made very strong of mahogany, and varnished over,
to make it perfectly tight.
A small glass vessel, capable of containing an
ounce measure, is used for measuring gases ; for
if this phial be successively filled, and inverted un-
der a large jar, we may thereby throw into that jar
any required quantity of an elastic fluid, or as many
measures of one elastic fluid, and as many of ano-
ther, as we please.
G (Fig. 7.), represents a tube for receiving a
mixture of gases that are to be exploded by the
electric spark. It is a very strong glass tube, closed
at one end, and having a scale upon it, cut with a
diamond. Near the closed end two wires pass
through the glass, and almost touch each other,
but not quite ; they are cemented in, so as to make
the holes air-tight. When this graduated tube is
filled with the fluid in the trough, and inverted
upon the shelf, certain measures of the gases to be
exploded are introduced in the usual way. If thus
the interval between the two wires be made a part
of the electric circuit, by fastening chains con-
PNEUMATO-CIIEMICAL APPARATUS. 15
nected with a Leyden phial to the rings of the
wires, the spark will pass through the interrupted
space between the two wires, and explode the
gases. These instruments are called ea:ploding
tubes.
In compound distillations, or when a decompo-
sition of the materials subjected to this process
takes place, and gases are formed, some of which
are absorbable by water, some by alkalis, and
others are not capable of being absorbed at all, it
is often required to preserve separate the several
new substances procured. The apparatus invented
by Lavoisier for this purpose is the most con-
venient.
A (Plate 2. fig. 1.), is a glass retort, the beak
of which is adjusted to a double tubulated balloon,
or receiver, B. To the upper tubulure of tliis re-
ceiver is fitted a glass tube, C, the other extremity
of which is conveyed into the Hquor contained in
the glass vessel, D : with this vessel, D, which has
three tubulures, are connected two or three other
similar vessels, by means of glass tubes fitted into
their tubulures, and to the last tubulure of the
range of vessels is adapted a glass tube which is
conveyed under a receiver placed upon the shelf
of the pneumatic cistern. Water is put into the
first of these vessels, caustic potash into the next,
or such other substances as are necessary for ab-
sorbing the gases, and the joinings are w^ell luted.
Sometimes it will happen that a re-absorption of
gas takes place; and in this case, that there may
be no danger of the water in the pneumatic tub
entering rapidly into the vessels through the tube,
E, a capillary tube is adapted to the middle tubu-
lure of each vessel, which goes into the liquid con-
l(i PNEUMATO-CHEMICAL APPARATUS.
tained in it. If absorption takes place, either in
the retort or vessels, the external air enters through
these tubes, to fill the vacuum which is occasioned
by the absorption, and no water comes into the
vessels.
Large vessels for containing air, and expelling
any given quantity, are called gazometers. They
are of various constructions ; one of the best is the
following : AB (fig. 2.), is a cylindrical vessel of
tin, japanned, nearly filled with water, and having
a tube, C, in the middle, open at top, and branching,
to communicate with the cock, D. Within this
vessel there is another cylindrical vessel, generally
of glass, of smaller size, F, open at bottom, which
is inverted and suspended by the lines e e, whicli
go over the pullies j^^^j^ and have weights^ o",
attached to them, to balance the vessel, F. While
the cock D remains shut, if the vessel F be pressed
downwards, the air included within it will remain
in the same situation, on the principle of the div-
ing-bell ; but if the cock be opened, and the vessel,
F, be pressed down, the air included within it will
escape through the cock, and if a blow-pipe be at-
tached to this cock, a stream of the gas may be
thrown upon lighted charcoal, or any other body.
By means of the graduated rod, //, also, the quan-
tity thrown out is exactly ascertained : this rod is
so divided as to express the contents of the inner
vessel in cubic feet, &c. This instrument also an-
swers for breathing any of the gases, by applying a
mouth-piece to the cock. To render it more
portable, the w^eights g gy are sometimes included
in the uprights i i, which aie hollow, and wide
enough to receive them. Sometimes, also, there
is another branch from the bottom of the pipe, m
PNEUMATO CHEMICAL APPARATUS. 17
the middle, directed to the side of the outer cy-
Hnder, and coming upwards by the side to the top,
where there is another cock attached.
For soliitiony and dissoluiionSy and for crystal-
lizing sails, vessels of glass or earthenware are
used.
The melting, or causing any body to pass from
the solid to the liquid state, by the action of fire,
is caWed Jiisi on. The fusion of metallic substances
requires vessels sufficiently strong to resist the fire.
Those vessels are mostly, if not always, made of
earthen-ware, or porcelain, or a mixture of clay
and powder of black-lead. They are called cru-
cibleSy and are generally of the forms represented
Tig. 3. Sometimes these vessels have covers made
of earthen-ware ; but sometimes the fused metal
must be exposed to a current of air : in that case,
the crucibles are broad and shallow, as at Fig. 4.
these are called cupels, and they are formed of
calcined bones, mixed with a small quantity of
clay, or of a mixture of clay and black-lead pow-
der. But the cupels must not be placed in a
closed furnace, or be surrounded by coals ; for, in
that case, the required current of air could not
have access to the fused metal. They are, there-
fore, placed under a sort of oven of earthen-ware,
which is called a miiffle, as represented, Fig. 5, which,
with the included cupel, is exposed to the heat of
a furnace.
The various degrees of heat which are required
for the performance of chemical operations render
a variety of fire-places, ov furnaces, necessary for a
chemist. Those furnaces are either open at top,
or they are covered with what is called a dome,
and have a chimney, or tube, to carry oft' the heated
VOL. 11, c
IS PNEUMATO CHEMICAL APPARATUS.
air, smoke, &c. They are sometimes supplied with
air from the natural action of the fire, which rare-
fies the air about the ignited fuel ; and the rarefied
air becoming specifically ligliter, ascends into the
chimney, whilst the colder, and consequently hea-
vier air, is forced by the atmosphere to enter at the
lower part of the furnace. Some furnaces are sup-
plied with air by means of bellows ; and those are
applied for forging iron, or for reducing metals
from the ore, which is called smelting. Hence the
furnaces derive their various names, and are called
simple^ or open furnaces^ reverheratory furnaces,
tvindy or air furnaces, blast furnaces, forges^ smelt'
ing furnaces, <§t.
A very useful kind of furnace, for many pur-
poses, is that invented by Dr. Black, of Edinburgh,
represented in Fig. 6. It consists of a cylindrical
or elliptical body of sheet-iron, coated within with
a mixture of loam and clay. The aperture A at
top is closed occasionally with an iron saucer full
of sand, which forms a sand-bath ; B is the door
of the fire-place, and C is the ash-pit register, which
slides so as to admit more or less air. D is an iron
tube which goes into the chimney of the room, to
carry off the smoke.
Blow-pipes are used for directing the flame of a
candle or lamp against any bit of ore or other sub-
stance required to be examined. They ought to
have a bulb upon the middle of their stem, to
contain the moisture that is formed from the breath.
See Fig. 7-
The blow-pipe contrived by Dr. Black, of a
conical form, represented in Fig. 8., is very con-
venient; a, is the nozzle.
When a solid substance, in powder or otherwise.
NOMENCLATURE OF CHEMISTRY. 19
is left for a certain time in a fluid, and the mixture -
is kept exposed to a slow degree of heat, the pro*
cess is called digestmi.
When one substance, which has an affinity to
another, is mixed with as much of that other
substance as its affinity will enable it to hold in
combination, then the former substance is said to
be saturated^ or the mixture to have attained the
point of saturation. If the mixture contain a
greater proportion of either substance, then that
mixture is said to contain an excess of it, or to be
surcharged. The same thing must be understood
of the compounds of more than two substances.
The dry way of performing chemical operations
is when strong degrees of lieat are used, and the
humid way is when fluid solvents are used.
Combustion is when a body is burned with the
assistance of respirable air.
Deflagration is when the combustion is attended
with little explosions or cracklings.
Detonation is a pretty loud report.
OF THE NOMENCLATURE OF CHEMISTRY.
One of the chief improvements which have been
made in modern chemistry has been the invention
of names for the compound substances, which ex-
, press the elements which enter into their compo-
sition, as well as the proportions in which those
elements are combined. By this the memory is
much assisted, in recollecting the nature of the
great variety of substances, and to which the an-
cient chemists gave arbitrary and frequently unap-
propriate appellations.
When the simple substances, oxygen, chlorine,
and iodine, which are supporters of combustion^
c ^
20 NOMENCLATURE OF CHEMISTRY.
enter into combination with each other, or with the
other elementary bodies, they form combinations
that are divided into two classes. In one class the
substances are ?iotacid, and their names have their
termination in ide, as oa:ide of chlorine, oJ^ide of
nitrogen, chloride of sulphur, iodide of iron, &c.
\VTien these supporters of combustion enter into
combination with a body in more than one propor-
tion forming oxides, the terminations, ous and ic,
are employed. Thus nitrogen, with the smallest
proportion of oxygen, forms the 7iitroiis oxide ;
and, with a large proportion, it makes the nitric
oxide.
When the metals combine with oxygen in one
proportion only, the compounds are called simply
oxides of the metals. Formerly the compound of
a metal with oxygen was called a caliv, as the calx
of tin, now the oxide of tin; and the process of
combining a metal with oxygen was called calcina-
tiojiy now oaigenation.
Sometimes oxygen can enter into combination
with a metal so as to form oxides in more than one
proportion, and then a syllable is prefixed to the
term oxide to denote that proportion ; the smallest
quantity of oxygen forms the protoj:ide of the me-
tal, the second quantity of oxygen makes the
deutoaide, and the third, the tritodide ; antl, far-
ther, the term peroxide is applied to that oxide of
the metal that contains the greatest proportion of
oxygen with which it is known to combine. The
same syllables are prefixed to chlorides and io-
dides.
An oxide combined with water is called a
hydrat.
When an acid is formed by the union of a simple
body with oxygen, it derives its name from that
NOMENCLATURE OF CHEMISTRY. SI
body ; as the sulphuric acid, which is formed of
sulphur and oxygen ; the carbonic acid, which is
formed of carbon and oxygen.
Sometimes oxygen will unite in several propor-
tions with a simple body, so as to form different
acids ; then the acid which is the most oxygen-
ated, has its termination in ic ; and that which is
the least oxygenated, in ous. Thus sulphur forms
two acids ; when it unites to the least proportion
of oxygen capable of making an acid, it forms the
sulphureous acidf and with a larger proportion of
oxygen it makes the sulphuric acid.
Hydrogen, like oxygen, combines with a certain
number of simple substances, and with them forms
compounds, some of which are acid, and others
are not. To distinguish the acids Jbrmed hy hy-
drogen, from those formed by oxygen, the former
are designated by the word hydro^ as the hydro-
chloric acid, hydro^uoric acid.
Products not acid, Jbrmed by hydrogen and a
simple substance, if solid, are called hydruret : if
gaseous, the name of the simple substance termin-
ated in ed is prefixed to that of hydrogen gas ;
as carburettedy or yhosphoretted hydrogen gas.
When chlorine, sulphur, phosphorus, and carbon,
unite to each other, or to another simple body,
the compound has also its termination in uret,
as chloruret of phosphorus, and of iron, sulphuret
of iodine, phosphuret of lime, carburet of iron, &c.
Neutral salts, or substances produced by the union
of acids and alkalis, are denominated from the
names of the acids and alkalis of which they are
composed. The salts produced by the acid whose
names end in ous have their terminations in ite ;
thus sulphurous acid and potash form sulphite of
potash : salts produced by acids ending in ic have
c 3
^ CALORIC.
their termination in ate : thus sulphuric acid and
potash form sulphate of potash, and so of all the
rest.
The terms, bi-sulphuret, bi-phosphoret, bi-sul-
phate, &c. denote that these compounds contain
twice as much sulphur, phospliorus, sulphuric
acid, &c. as the sulphuret, phosphoret, sulphate, &c.
CALORIC.
C4.L0RIC, or the matter of heat, is generally con-
sidered as a peculiar elementary substance. It
cannot be ascertained to have any weight, a body
when heated not being heavier than before.
A distinction is made between caloy^ic, or the
njiatter of heat, and the word heat when considered
as a sensation. The sensation of heat, or sensible
heati is the eifect produced upon our organs by the
motion of caloric disengaged from the surrounding
bodies. Whei> we touch a cold substance, the
caloric^ which e?cists in unequal quantities in dif-
ferent bodies, but which always tends to be in equi-
librio in all bodies, passes out of the hand into the
body, which feels cold, because at the time there
w^s less free caloric in the substance than in the
hand ; and as we have lost heat, we feel the sensa-
tion of cold : cold being, not any thing positive, but
merely the want of heat. The contrary happens
"vyhen we touch a warm body j the caloric then in
passing into the hand, gives the sensation of
warmth. If the hand and the body touched be of
the same temperature, or very nearly so, we re-
ceive no impression either of heat or cold, because
there is no motion of caloric.
l^yfree caloric, we mean that which is not com-
bined with any other body. But, as caloric has a
CALORIC. ^S
very strong tendency to combination, we are not
able to procure it in that state.
Combhied caloric is that which is fixed in bodies
by affinity or elective attraction, so as to form
part of their constitution. By the expression spe-
cific caloric of bodies, we understand the respective
quantities of caloric requisite for raising bodies of
the same weight to an equal degree of temperature.
This proportional quantity of caloric is thought to
depend upon the distance between the consti-
tuent particles of bodies, and their greater or less
degrees of cohesion ; and this distance, or rather
the space or void resulting from it, is called the ca-
pacify of bodies for heat.
Heat has the property of expanding bodies, or
increasing their bulk. This may be observed by
fitting a piece of iron to an iron ring so as just to
fill it : then if the iron be heated in the fire, it wdll
be found that it has become too large to pass
through the ring ; but when cooled, it contracts
to the same size as before. Some metals will ex-
pand more than others.
It is supposed that the caloric forces itself be-
tween the particles of bodies so as to separate
them. In acting thus, it is in direct opposition to
the attraction of cohesion, which keeps them
together.
Fluids also expand by heat. Put water into a
very small glass tube with a bulb, and apply heat
to the bulb ; the water will be seen to expand and
fill more of the tube : as it cools, it will contract
again.
Gases also increase in volume, by increase of
temperature. Tie the neck of a bladder tight ;
when it is almost empty, lay it before the fire ; the
included air will expand, and the bladder will swell
c 4
24t . "- CALORIC.
and appear full, but will return to its former state
by withdrawing it from the fire. From this pro-
perty of matter in expanding by heat, the thermO"
meter becomes a measure of the heat in bodies.
Every body, therefore, whether solid, liquid, or
gaseous, is augmented in all its dimensions, by an
increase of sensible heat : and on the contrary, all
bodies contract by an abstraction of caloric. We
are still very far from being able to produce the
degree of absolute cold, or total deprivation of
heat ; hence, we are incapable of causing the ulti-
mate particles of bodies to touch each other.
It may be supposed, since the particles of bodies
are thus constantly impelled by heat to separate
from each other, that they would have no con-
nexion between themselves ; and that, of conse-
quence, there could be no solid body, unless the
particles were held together by some power which
tended to unite them ; this power is the attraction
of cohesion. Thus, the particles of all bodies
may be considered as subject to the action of two
opposite powers, repulsion and attraction^ between
which they remain in equilibrio. So long as the
attractive force remains strongest, the body must
continue in a state of solidity ; but if, on the con-
trary, heat has so far removed these particles from
each other, as to place them beyond the sphere of
attraction, they lose the cohesion they had before
with each other, and the body ceases to be solid.
Water gives us a regular and constant example
of these facts. Whilst below 32° it remains solid,
and is called ice. Above that degree of temper-
ature, its particles being no longer held together by
reciprocal attraction, it becomes liquid ; and when
we raise its temperature above 212**, its particles
giving way to repulsion caused by the heat, assume
\
CALORIC. 25
the state of vapour or gas^ and the water is
changed into an aeriform fluid.
The same may be affirmed of all bodies in na-
ture. They are either solid, or liquid, or in the
state of elastic aeriform vapour, according to the
proportion which takes place between the attrac-
tive force inherent in their particles, and the re-
pulsive power of heat acting on them ; or, what
amounts to the same thing, in proportion to the
degrees of heat to which they are exposed. But
were there no other cause affecting the solidity of
bodies except the powers of attraction and repul-
sion, they would become liquid at an indivisible
degree of the thermometer, and would almost in-
stantaneously pass from the solid state of aggreg-
ation to that of aeriform elasticity. Thus water,
for instance, at the very instant when it ceases to
be ice, would begin to boil, and would be trans-
formed into an aeriform fluid, having its particles
scattered indefinitely through the surrounding
space. That this does not happen, must depend
upon the action of some third power. The pres-
sure of the atmosphere prevents this separation,
and causes the water to remain in the liquid state
until raised to the temperature indicated by SIS'^ ;
the quantities of caloric, which it receives in the
lower temperatures, being insufficient to overcome
the pressure of the atmosphere.
Whence it appears, that, without this atmos-
pheric pressure, we should not have any permanent
liquid, and should only see bodies in that state in
the very instant of melting ; for the smallest addi-
tion of caloric would then instantly separate the
particles, and dissipate them through the surround
ing medium. Besides, without this atmospheric
pressure, we should not even have any proper aeri-
96 CALORIC.
form fluids ; because the force of attraction
would be overcome by the repulsive power of
caloric ; and the particles of bodies would separate
themselves indefinitely, having nothing to give
limits to their expansion, unless their own gravity
might collect them together so as to form an
atmosphere.
It may be admitted, therefore, as a general prin-
ciple, that almost every body in nature is suscep-
tible of three several states of existence, soUd^
liquid, and aeriform ; and that these states depend
upon the quantity of caloric combined with the
body.
The elastic aeriform fluids are expressed by the
generic name of gas ; and in each species of gas,
a distinction is made between the caloric, which,
in some measure, serves the purpose of a solvent,
and the substance which, in combination with the
caloric, forms the base of the gas. Thus water,
united to a sufficient quantity of caloric, is called
aqueous gas ; ammoniac saturated with caloric, is
called ainmoniacal gas, he.
Caloric, when free, appears to move in the form
of rays, and to be capable of being reflected in the
same manner as light. The calorific part of the
solar rays, or those which occasion heat, are con-
densed by a lens, ora mirror, as well as those which
produce light; and the rays of heat from any burn-
ing body, or even of a body heated, although not
in a state of combustion, are thrown off in a radiat-
ing manner. If two polished metallic mirrors be
placed opposite to each other, at several feet dis-
tance, and if a pan of burning coals, or a heated
piece of iron, be held in the focus of one of them, a
thermometer placed in the focus of the opposite
one, will be immediately affected as if it had been
CALORIC. %J
held close to the heated matter ; and this will be
the case, even if the heated body is not luminous or
incandescent, as hot water, for instance; so that the
invisible rays of heat also are reflected like those of
light. The chief part of the heat received from a
common fire is in the form of radiant heat ; and
whatever kind of construction will most promote
the reflection of radiant heat into the room, will be
the most advantageous form of the chimney. It is
upon this principle that the grates introduced into
common use by Count Rumford are so much pre-
ferable to all others.
The effect of the solar rays upon bodies differs
much according to their colour ; black and dark
coloured bodies are more heated than white ones ;
the latter throwing off" the rays, while the former
absorb them. For this reason, black clothes are
more heated by the sun than white ones. Polished
surfaces, also, which reflect best, do not absorb so
much heat as rough surfaces.
The boiling or ebullition of liquids is a phenome-
non which depends upon the liquid being converted
into vapour by a certain degree of temperature ;
consequently, those liquids which assume the va-
porous or aeriform state at the lowest temperature
are most easily made to boil. The ebullition, or
the noise and motion of the liquid in boiling, is
occasioned by small quantities of vapour being
formed at the bottom of the vessel, which rise by
their lightness in a globular form, and break at the
surface. The ebullition of liquids is easier in pro-
portion as the pressure to which they are subjected
is less ; thus water, which boils only at 212° Fahr.
in the air, will boil with a much less degree of heat
in an exhausted receiver of the air pump ; and it
28 CALORIC,
will also boil with much less heat on lofty moun-
tains than in the valleys.
Bodies differ very much with respect to the fa-
cility with which heat passes through them. Those
which transmit caloric easily are called conductors
of caloric ; and, according to the power of doing
so, they are termed good or bad conductors.
Those which do not transmit heat at all, or with
great difficulty, are called non-conduct07^s. How-
ever, it should be observed, that, perhaps, no
substances are absolutely non-conductors ; but
liquids and gases admit the passage of caloric
through them with such great difficulty, that, for
practical purposes, this division is found useful.
Liquids carry heat chiefly by transportation ; the
part of the liquid that is heated rises to the sur-
face, and gives place to another which is warmed
in its turn, and so on until the whole has been
heated.
Many very important applications of this prin-
ciple have been made by Count Rumford to oeco-
nomical purposes. He showed that a stratum of
confined air was one of the best modes of prevent-
ing the escape of heat.
The best conductors of heat are metals, and the
best non-conductors are fluids and porous sub-
stances. Charcoal is an excellent non-conductor.
Heat may be excited by mere friction ; and this,
probably, was the earliest mode of obtaining it to
procure fire. It is still practised among uncivilized
nations. For this purpose they take two pieces of
dry wood, one about eight or nine inches long,
and the other piece quite flat. They cut a blunt
point upon the first, and, pressing it upon the
other, they whirl it round very quickly, holding it
CALORIC. 29
oetween both their hands, as we do a chocolate
mill. In a few minutes the wood takes fire. If
the irons of the axle of a coach-wheel be left with-
out grease or oil, they will become so hot as to set
fire to the wheels j and accidents of this kind some-
times happen.
It is no uncommon practice in the country, for
a blacksmith to hammer a piece of iron till it be-
comes red hot, as a substitute for a tinder-box.
The heat excited by the boring of a cannon is suf-
ficient to cause water to boil.
Heat is also produced by collision ; when a
piece of hardened steel is struck with a flint, some
particles of the metal are broken off, and so violent
is the heat produced by the stroke, that they are
rendered red hot, and melted. If the fragments
of steel be caught upon a piece of white paper and
examined with a microscope, they will be found to
be spherules, and highly polished, showing that they
had been fluid.
No heat seems to follow from the percussion of
liquids in soft bodies.
The instruments for measuring heat by the ex-
pansion of bodies are, thermometers for fluids, and
pyrometers for solids.
A thermometer is a hollow tube of glass, her-
metically sealed, and blown at one end into the
shape of a hollow globe, or bulb. The bulb and
part of the tube are filled with mercury, which is
the only fluid that expands equally. AVhen we im-
merse the bulb of the thermometer in a hot fluid,
the mercury expands, and, of course, rises in the
tube; but when we plunge it into a cold body, the
mercury contracts, and, of course, falls in the tube.
The rising of the mercury, therefore, indicates an
increase of heat ; its falling, a diminution of heat.
30 cALonic.
To facilitate the observation, the tube is divided
into a number of equal parts, called degrees, or
there is a divided scale attached to it.
This scale is graduated in different manners by
different nations : Fahrenheit's scale is that al-
ways used in this country.
The standard points are obtained by freezing
and boiling water, degrees of heat which are con-
stantly the same in nature. The heat at which
the mercury stands, when immersed in each, being
marked, the distance between them is divided into
180 parts, and 32 parts of the same size are con-
tinued downwards, so that 32° shows the heat of
freezing water, and 212° that of boiling water.
AVater cannot be made hotter than this in open ves-
sels, because it then becomes converted into steamy
or aqueous gas.
The mercurial thermometer, it is evident, cannot
measure degrees of heat above that of boiling mer-
cury, nor below that of freezing mercury ; the
former is 600°, and the latter 40° below 0 of Fah-
renheit's scale.
For greater degrees of cold, thermometers of
spirits of wine, or essential oil, are used ; and to
measure those higher degrees of heat to which the
thermometer cannot be applied, pyrometers are em-
ployed. An instrument of this kind was invented
by the late Mr. Wedgewood. It consists of two
pieces of brass, fixed so as to form an angle, having
the legs divided into equal parts. Pieces of baked
clay are prepared for this scale, so as to fit the
brass at a certain place. If then the piece of
clay be exposed to the heat required to be ex-
amined, it will contract in its dimensions, and,
when again applied to the brass scale, it will be
seen how much it has contracted. By this the in-
CALORIC. 31
tensity of the heat is ascertained, for the clay of
which these pieces are prepared, has the property
of contracting regularly, according to the degree
of heat.
This is an exception to the general law of bodies
expanding by heat ; the expansion of melted metal
in the act of cooling is another, as likewise the ex-
pansion of water in the act of freezing.
The greatest degrees of heat which can be raised
have been produced by concentrating the solar
rays with a mirror or lens, or by supplying a blow-
pipe with oxygen gas ; or, what is still more power-
ful, by a mixture of oxygen and hydrogen. This
last method has been but lately employed, and pro-
duces a far greater degree of heat than any other.
The mixture is itself of an explosive nature, and,
therefore, without proper precaution, exceedingly
dangerous. The greatest degree of cold known to
have been produced has been obtained by mixing
snow with certain salts. The best salt for this
purpose is muriat of lime. If this be mixed with
dry light snow, and stirred well together, the cold
produced will be so intense as to freeze mercury in
a few minutes. Salt and snow also produce a great
degree of cold.
Evaporation, likewise, produces cold. The me-
thod of making ice artiiicialiy in the East Indies
depends upon this principle. The ice-makers at
Benares dig pits in large open plains, the bottom
of which they strew with sugar-canes, or dried
stems of maize, or Indian corn. Upon this bed
they place a number of unglazed pans, made of so
porous an earth that the water oozes through their
substance. These pans are filled towards evening,
in the winter season, with water v.'hich has been
boiled, and are left in that situation till morning,
S^ CALORIC.
when more or less ice is found in them, according
to the temperature of the air ; there being more
formed in dry and warm weather than in cloudy
weather, though it may be colder to the human
body.
Every thing in this operation is calculated to
produce cold by evaporation ; the beds on which
the pans are placed suffer the air to have a free
passage to their bottoms, and the pans, constantly
oozing out water to their external surface, are
cooled by the evaporation of it.
In Spain, they use a kind of earthen jars called
buxaros, the earth of which is so porous, being
only half baked, that the outside is kept moist by
the water which filters through it ; and, though
placed in the sun, the water in the jar becomes as
cold as ice.
It is a common practice in China, to cool wine,
or other liquors, by wrapping a wet cloth round
the bottle, and lianging it up in the sun. The
water in the cloth evaporates, and thus cold is pro-
duced.
Ice may be produced, at any time, by the eva-
poration of ether. Take a thin glass tube, four or
five inches long, and about two or three eighths of
an inch in diameter, and a two-ounce bottle of
ether, having a tube drawn to a point, fitted to
its neck. Pom- some water into the glass tube,
and let a stream of ether fall upon that part of
it containing the w^ater, which, by that means, will
be converted into ice in a few minutes. If a thin
spiral wire be introduced into the tube before the
water is poured in, the ice will adhere to it, and
may be drawn out.
33
LIGHT.
Under Optics, the mechanical properties of light
were considered.
Light has considerable influence on chemical
operations, but little is known of its real nature.
Most generally it is considered as a certain simple
substance, of which the chief source is the sun ;
and it is also disengaged during the processes of
combustion.
The most delicate experiments have been insti-
tuted for the purpose of discovering whether it
has weight, but without success ; on which account
it is reckoned among the imponderable bodies. -
There appears to be an intimate connexion be-
tween light and heat, and they are frequently
given out together. But although they are both
always found in the sun's rays, yet from them
they may be obtained separately, the iusisible rays
of heat being more refrangibible than those of
light : see vol. i.
Light is capable of entering in union with many
substances, and of being again separated from
them. This is the case in the substance called
pyrophorus, which is made by exposing to a red
heat in a crucible for some time, a mixture of
pounded oyster shells and sulphur. If this sub-
stance be then carried into the light for a few
seconds, it will imbibe so much that it will become
luminous in the dark by again giving out this light.
Various kinds of meat, but particularly fish
when they are beginning to putrefy, also rotten
wood, sea-weeds, and some insects, as the glow-
worm and lanthorn fly, have the property of shining
in the dark.
VOL. II. D
34 LIGHT.
The effect of light upon vegetation is well
known. Many flowers follow the course of the
sun, and most flowers turn themselves more or less
towards the light. Plants that grow in darkness
are pale and without colour, and when this is the
case they are said to be etiolated, or blanched.
Gardeners avail themselves of this fact to render
some vegetables, as celery and endive, white and
tender. The more plants are exposed to the light,
the more colour they acquire. Vegetables are
not only indebted to light for their colour, but
their taste and odour are derived from the same
source. From this it happens, that hot climates
are the native countries of perfumes, odori-
ferous fruits, and aromatic resins. The action of
light on the organs of vegetables causes them to
pour out streams of oxygen gas from the surfaces
of their leaves, while exposed to the sun, whereas,
on the contrai'y, when in the dark, they emit air
of a noxious quality.
Animal life seems also to be no less influenced
by light. Birds that inhabit tropical countries
have much brighter plumage than those of the
north. Animals in general seem to droop when
deprived of light ; and no doubt it is \Qry essential
to the health of human beings.
The colour of metallic oxides is changed by the
action of light : the yellow oxide of tungsten be-
comes blue by exposure to hght ; the white salts
of silver become black, and green precipitate of
iron becomes red. Some oxides of metals lose
w^eight by exposure to light, as the red oxide of
mercury ; others lose their oxygen entirely, or
become reduced, as the oxide of gold. Light,
tlien, has the property of separating oxygen from
several of the oxides.
ELECTRICITY. 35
Some substances when heated to a certain de-
gree become luminous ; iron, for instance ; and
this is what is called a red heat.
If bodies heated to redness be introduced into a
gas, it does not become visible, and hence it has
been concluded that gas is not capable of being
made luminous : but it is now considered that
flame is hydrogen gas in a luminous state.
Light is also produced by percussion ; as in the
case of a flint and steel. The spark produced in
this case is owing to the flint breaking off a small
fragment of the steel, which is thus rendered red
hot, and burns diu'ing its passage through the air.
But two pieces of quartz struck smartly toge-
ther also give out light, although here there can
be no combustion.
Instruments for measuring the degree or inten-
sity of light are called photometers,
ELECTRICITY.
Electricity and galvanism have been already
treated of in the first volume. The electric fluid
is now considered as a chemical agent of great
importance, exciting a powerful influence in the
decomposition of bodies. The connexion between
electricity and chemical decomposition was first
shown by Sir Humphry Davy, to whom the world
is indebted for so many brilliant discoveries.
There is still, however, great uncertainty and
various opinions with respect to the real nature of
this influence, which is usually classed among the
imponderable elementary bodies.
D 2
Si)
OXYGEN.
Oxygen is an elementary body that cannot be
procured in a separate or free state, that is, it cannot
be detached from tlie other bodies with which it is
always combined.
Oxygen gas is so called from two Greek words,
signifying the generator of acids, because it was
considered by Lavoisier as the only acidifying
principle. It has been called also piu^e or vital air.
About one fourth of the atmosphere consists of
this gas, and it is essential to respiration and animal
life. It is the most powerful and general supporter
of combustion ; and by its union with other bodies^
it forms most of the acids. Oxygen gas may be
easily procured by several processes.
1. It is obtained in the greatest purity from
oxy-muriate of potash. Put some of this salt into
a small glass retort, place the neck under the shelf
of the pneumatic trough, and apply the heat of a
lamp to the retort. The salts will soon melt and
boil, when oxygen gas will come over in great
abundance.
Q.. Black oxide of manganese is usually employed
for furnishing this gas, as it affords it at a cheaper
rate. Procure an iron retort made for the purpose,
fill it with the oxide, fit a conducting tube to it,
and place the retort between the bars of a grate
which contains a good fire. Keep up the heat
until the retort becomes red hot, and the gas will
be received in the pneumatic apparatus. Or it
may be made from oxide of manganese, put into a
^lass retort, with half its weight of strong sulphuric
OXYGEN. 37
acid. It may be likewise obtained in great quan-
tity from nitrat of potass (salt petre) in an earthen
retort exposed to a strong fire ; also from the red
oxide of lead, heated with or without sulphuric acid.
Having procured a sufficient quantity of this
gas in separate vessels, its properties may be easily
examined.
It will be found that water does not absorb it ;
for if some of it be agitated in a small vial half filled
with water, and again immersed into the trough,
it will not be diminished in quantity ; nor will the
water rise in an inverted vessel of this gas, if left
on the shelf of the trough for a day.
Oxygen gas is eminently calculated to support
the combustion of bodies. Plunge a lighted taper
fixed to an iron wire, or a lighted splinter of wood,
and the combustion will proceed with a splendour
much encreased.
The flame of a lamp urged by a stream of oxygen
gas, - instead of common air, excites a heat more
intense than the hottest furnace.
Even the metals Which are not easily combustible
in common air burn in oxygen gas with great readi-
ness. Iron or steel wire burns in a very striking
manner. It should be kindled by having a small
bit of w^ood fastened to the point ; the combustion
of this will communicate to the steel wire, which
will continue to burn. The fused drops of iron
that fall down, when examined, will be found to be
no longer malleable, but brittle and converted into
the oxide of iron. The same change will take
place when the other metals are burnt in this gas.
If a piece of charcoal, fixed to an iron wire, be
lighted by a blow pipe, and put into ajar of oxygen
gas, it will burn with a brilliant light, and throw
D 3
38 NITROGEN.
out numerous sparks, exhibiting a very beautiful
appearance. Here the combustion pi'oduces a
combination of" the oxygen with the carbon of the
charcoal, and the result is carbonic acid.
A small bit of phosphorus, put into a copper
spoon, burns in this gas with a light intensely
bright. It is necessary to inform the young prac-
titioner, that this experiment must be made with
great caution. The phosphorus must be cut under
water, and the piece employed must not exceed
half the size of a small pea. The glass jar, in
which the combustion is made, is not unfrequently
broken by the heat. The result of this combustion
is the phosphoric acid, from the combination of the
phosphorus with the oxygen.
In all these cases, if the products of the com-
bustions be carefully weighed, it will be found to ex-
ceed that of the substances burned, and the oxygen
will be diminished, which shows they have ab-
sorbed a quantity of the oxygen employed. But
this is still further proved, because the oxygen
may be extracted from these newly-formed com-
pounds, and the original bodies will be thus made
to re-appear.
If the metal potassium, or sodium, be burned in
oxygen, they form, by their union with it, the alka-
lis, potass and soda ; so that oxygen is not only an
acidifying^ but an alkalising principle.
Oxygen appears to be connected with the cause
of the red colour in blood, for if dark coloured
blood be put into a phial of oxygen gas and shaken,
the blood will assume a bright red colour.
S9
NITROGEN.
Nitrogen gas is so called, because its base'
forms nitric acid by its union with oxygen. It was
by Lavoisier named azotic gas, and its base azote,
from a Greek word signifying without life, because
it is entirely destructive to animal life.
This, also, though a very abundant principle,
cannot be exhibited in a free or uncombined state.
In the state of gas, it forms a considerable part
of our atmosphere ; - in the solid state it enters into
the composition of animal and vegetable bodies,
nitric acid, and ammonia. It is incapable of sup-
porting combustion or animal life. It is not ab-
sorbed by water, and it has no acid properties.
It may be obtained by separating the oxygen
from a portion of the atmospheric air ; the residue
will be nitrogen. This is done by exposing a cer-
tain quantity of atmospheric air to sulphuret of
potass, which absorbs the oxygen, leaving the
nitrogen free.
It may be also obtained by treating muscular
flesh, (as lean veal) with nitrous acid in a retort ; the
flesh is decomposed, and the nitrogen set at liberty.
That it does not maintain combustion, and is fatal
to animal life, may be proved by plunging a lighted
taper into a vessel filled with this gas, the taper will
be immediately extinguished. If a small animal,
as a mouse, or a bird, be immersed in it, it im-
mediately dies.
D 4
40
COMBINATIONS OF OXYGEN AND NITROGEN.
Nitrogen and oxygen unite together in four
different proportions :
1. Nitrous oxide, in which the oxygen is but
half the vokime of the nitrogen.
2. Nitric oxide, in which the volumes of oxygen
and nitrogen are equal.
3. Nitrous acid, in which the volume of oxygen
is twice the volume of nitrogen.
4. Nitric acid, in which the oxygen is two and a
half times the volume of nitrogen.
Nitrons oxide. This gaseous compound, called
also the gaseous odide of nitrogen, or the gaseous
oxide of azote, was first discovered by Dr. Priestley ;
but it is to Sir Humphry Davy that we owe a
tliorough knowledge of its properties.
Nitrous oxide is a permanent gas. A candle burns
in it with a brilliant flame and crackling noise ; be-
fore its extinction, the white inner flame becomes
surrounded with a blue one. Phosphorus intro-
duced into it, in a state of inflammation, burns with
increased splendour, as in oxygen gas.
Sulphur, introduced into it when burning with a
feeble blue flame, is extinguished ; but when in a
state of vivid inflammation, it burns with a rose-
coloured flame. Lighted charcoal burns in it more
brilliantly than in atmospheric air.
Iron wire, v/ith a small piece of wood affixed to
it, and introduced inflamed into a vessel filled with
this gas, burns rapidly, and throws out bright scin-
tillating sparks.
Nitrous oxide is rapidly absorbed by water that
has been boiled, and a quantity of gas equal to rather
more than half the bulk of the water may be thus
COMBINATIONS OF OXYGEN AND NITROGEN. 41
made to disappear ; the water acquires a sweetish
taste, but its other properties do not differ per-
ceptibly from common water. The whole gas
may be expelled again by heat.
It does not change blue vegetable colours. It
has a sweet taste, and a faint, but agreeable odour.
This gas explodes with hydrogen, when electric
sparks are made to pass through the mixture.
Animals, when confined wholly in this gas, give
no signs of uneasiness at first; but they soon be-
come restless, and then die.
When it is mingled with atmospheric air, and
then received into the lungs, it generates highly
pleasurable sensations. The effects it produces on
the animal system are very extraordinary ; it ex-
cites the body to action, and rouses the faculties of
the mind, inducing a state of great exhilaration,
an irresistible propensity to laughter, a rapid flow
of ideas, and unusual vigour and fitness for muscu-
lar exertions, in some respects resembling the sen-
sations attendant on intoxication, without any lan-
guor or depression of spirits, or disagreeable
feelings afterwards ; but more generally followed
by vigour and a disposition to exertion, which
gradually subsides.
This gas is produced when substances having a
strong affinity with oxygen are added to nitric acid,
or to nitrous gas. It may, therefore, be obtained by
various methods, in which nitrous gas or nitric acid
is decomposed by bodies capable of attracting the
greater part of their oxygen. The most commo-
dious and expeditious, as well as cheapest mode
of obtaining it, is by decomposing nitrate of ammo-
nia by heat, in the following manner : put into a
glass retort some pure nitrate, and apply to it
an ArgaQd's lamp ; the salt will soon liquify, and
42 COMBINATIONS OF OXYGEN AND HYDROGEN.
when it begins to boil, gas vviJI be evolved. Increase
the heat gradually, till the body and neck of the
retort become filled with a milky white vapour. In
this state, the temperature of the fused nitrate is
between 340 and 480°. After decomposition has
oroceeded for some minutes, so that the gas, when
examined, quickly enlarges the flame of a taper, it
may be collected over water. Care should be taken,
during the whole process, never to suffer the tem-
perature of the fused nitrate to rise above 500^ of
Fahrenheit; which may be easily judged of from
the density of the vapours in the retort, and from
the quick ebullition of the fused nitrate ; for if the
heat be increased beyond this point, the vapours in
the retort acquire a reddish and more transparent
appearance, and the fused nitrate begins to rise,
and occupy twice the bulk it did before. The
nitrous oxide, after its generation, should stand
over water for several hours; it is then fit for
respiration or other experiments.
The explanation of this process is as follows:
Nitrate of ammonia consists of nitric acid and
ammonia ; nitric acid is composed of nitrous gas
and oxygen ; and ammonia consists of hydrogen
and nitrogen. At a temperature of 480°, the
attractions of hydrogen for the nitrogen in the
ammonia, and that of nitrous gas for the oxygen
of the nitric acid, are diminished; while, on the
contrary, the attractions of the hydrogen of the
ammonia for the oxygen of the nitric acid, and
that of the remaining nitrogen of the ammo-
nia for the nitrous gas of the nitric acid, are in-
creased; hence all the former affinities are broken,
and new ones produced; namely, the hydrogen of
the ammonia attracts the oxygen of the nitric acid,
the result of which is water. The nitrogen of the
NITRIC OXYDE. 43
ammonia now combines with the disengaged nitrous
gas, and forms nitrous oxyd.
To experience its effects in breathing it, put
about a gallon into a large bladder, or oiled silk
bag, having a tube attached to it, of three-fourths
of an inch in diameter. First, the common air
must be expelled from the lungs, before the tube
is received into the mouth, and the nostrils must be
accurately closed with the hand. It must then be
breathed backwards and forwards into the bag for
a few minutes.
Nitric Oxyde is called also nitrous gas. This com-
pound of oxygen and nitrogen cannotbe obtained by
direct combination, but by abstracting from nitric
acid a portion of its oxygen, leaving the remainder
in such proportion as to constitute nitric oxide.
When pure, it is not acid, and is void of colour.
It is incapable of supporting the combustion of
most bodies; nevertheless, phosphorus and pyro-
phorus burn in it. Nitrous gas is made by putting
clippings or filings of copper into a retort with
nitric acid, diluted with thrice as much water ; red
fumes will be given out, if the gas is suffered to
escape into the air ; but if collected in the pneu-
matic apparatus, the gas is colourless. In this pro-
cess, the metal attracts the oxygen from the nitric
acid, and becomes oxydated ; the rest of the acid
being deprived of a great portion of its oxygen, can
no longer exist as acid ; it therefore expands, be-
comes aeriform, and appears as nitrous gas.
When nitrous gas and oxygen gas are mixed to-
gether in a glass vessel, previously exhausted of air,
they instantly unite, and form a reddish coloured
gas, which has but half the volume of the two gases,
and which is highly acid. This new compound is
called nitrous add gas.
44 NITROUS ACID.
Nitrous acid gas is very easily absorbed by
water, rendering it a green, sour liquid.
When nitrous gas is mixed with atmospheric air,
the same red fume appears, from the nitrous gas
uniting to the oxygen of the atmosphere, leaving
the nitrogen by itself. Hence this gas has been
used for measuring the quantity of oxygen gas con-
tained in air, and an instrument for this purpose
has been called an Eudiometer. A tall glass tube,
sealed at one end, is used for this purpose, filled with
water, and inverted in the pneumatic apparatus.
Send up a certain measure of the air to be examined
into this tube, and mark the space which it occu-
pies in the top of the tube. Then add to it a mea-
sure of nitrous gas, and observe the degree of
diminution. By comparing how much different
specimens of air will be di"minished by the same
quantity of nitrous gas, the relative quantities of
oxygen in each may be estimated. This method of
analysing atmosphere is not considered as very cor-
rect, and other modes are sometimes used, where
there are fewer sources of inaccuracy.
Nitrous Acid.
Considerable uncertainty prevails respecting this
acid. The yellow coloured fuming acid, to which
this name has been given, appears to be only nitric
acid holding nitrous gas in solution. The nitrous
gas may be expelled from it by the application of
heat, and then the nitric acid is left colourless.
But if nitrous gas and oxygen gas be mixed
together, without the access of water, by intro-
ducing them into a vessel previously exhausted of
air, an union takes place ; the two gases diminish
to half the volume, and an acid gas is produced.
NITKIC ACID. 45
This is the nitrous acid in a gaseous form. This
acid gas is extremely absorbable by water, which is
at first rendered green : then, as the absorption goes
on, it becomes blue, and, finally, of an orange
colour : by adding more water, it may be brougTit
back to the green colour.
If dry nitrate of lead be distilled, an orange-
coloured liquid comes over; which is considered as
nitrous acid nearly pure.
Nitric Acid.
This acid is one of those which have been longest
known to chemists. It is so named from nitre,
from which it was procured. The corrosive acid
called aqua fortis is an impure and weak nitric
acid: but it was long used before its analysis was
known: this we owe to Cavendish.
NitrCi called also saltfetre^ consists of this acid
united with potass, and the process for procuring the
acid depends upon decomposing this salt. For this
purpose, some substance is added to the nitre that
has an attraction for the potass sufficiently strong to
overcome that of the nitric acid, and, consequently,
to allow it to be expelled by heat. Sulphuric acid
is used for this purpose. During its expulsion,
however, the nitric acid suffers a partial decompo-
sition ; for though it is nitric acid that exists in the
salt, it is nitrous acid that condenses in the receiver
in the form of orange fumes. This is the common
nitrous acid of commerce.
To convert this into nitric acid, another process
is necessary. By distillation, nitrous acid gas is
driven off, leaving the nitric acid colourless. Or,
40 ATMOSPHERIC AIR.
it is distilled on black oxide of manganese, which
gives more oxygen to it.
Nitric acid is extremely caustic; that is, acts
powerfully upon animal substances. It unites with
the alkalis and earths ; it oxidates all the metals
except gold and platina ; it thickens and blackens
oils, converting them into a coal, or inflaming
them, according to the nature of the oil, and the
degree of the concentration of the acid.
The combinations of nitric acid with different
bases are called nitrates.
When the nitrogen and oxygen gases are mingled
together, they form a compound exactly resembling
common or atmospheric air.
Atmospheric Air
Is, indeed, essentially composed of these two gases:
and its analysis or decomposition has been one of
the most interesting discoveries of modern che-
mistry. It is curious that one of the ingredi-
ents of this substance, so necessary to animal life,
should, by itself, be highly deleterious.
It has been completely proved, that the air of
the atmosphere is a compound body, formed by the
mixture of oxygen gas and nitrogen gas. The first
is the only one of them that supports combustion ;
and when combustion takes place in common air,
it is this part that unites to the burning body, form-
ing either an oxide or an acid. If mercury be
heated in a given quantity of atmospheric air for
some time, it will become changed into a red pow-
der, which will weigh more than the mercury ; the
air will be found to be diminished in quantity, and
13
ATMOSPHERIC AIR. 4^
to be no longer capable of supporting combustion.
The reason of this is, that the oxygenous part of
the air has united to the metal, and converted it
into an oxyde, leaving behind only the nitrogen.
This decomposition of the atmospheric air may
be effected more easily by burning phosphorus in
it. During the combustion of the phosphorus, it
unites to the oxygen, and forms phosphoric acid j
the remainder is nitrogen.
The proportion of oxygen gas contained in a
given quantity of atmospheric air can be ascertain-
ed by various processes. One method is, by in-
verting a glass tube into a solution of sulphuret of
potass. This substance will absorb the oxygen
gas, but not the nitrogen ; hence the air in the
tube will diminish in bulk, and what remains will
show the proportion of nitrogen.
It was supposed by modern chemists, until lately,
that oxygen was essential to combustion ; and that
this process was, in all cases, the combination of
oxygen with the combustible body; but it has
been found, that there are some other substances,
as chlorine and iodine, which have also this pro-
perty of supporting combustioii : it is, however, the
oxygen that acts in all the usual combustions in
common air. The heat and light were supposed
to be separated from oxygen, the base of the gas,
which became fixed in the burned body. At pre-
sent it is maintained by some, that combustion
may be the consequence of intense chemical ac-
tion, and need not depend upon any particular
combination. This subject, however, remains very
obscure.
Air, which has been breathed, is found to have
lost its oxygen. This principle is retained in the
48 ATMOiSPHERIC AIR.
Jungs, and is absorbed into the blood: it appears
essentially necessary to vitality.
An animal can only live for a limited time in a
given portion of air. If a mouse or a bird be con-
fined under a glass that is closed, they will soon
die ; a candle, also, will burn only a short time. In
crowded rooms, where there is not a free circula-
tion of air, the oxygen is diminished by the respi-
ration of so many persons, and the air is rendered
unhealthy. The lights, also, are observed to burn
dim, and contribute much to exhaust the oxygen.
This points out the importance of ventilating
all kinds of apartments, but particularly public
places.
It has been found that in 100 parts by measure
of atmospheric air, there are 21 parts of oxygen
gas and 79 of nitrogen gas.
From the property of oxygen as being essential
to respiration and animal life, it had been thought
that the salubrity of air must depend upon the
quantity of oxygen which it contained ; but, al-
though the airs of various places have been ex-
amined, as that of towns, prisons, the country,
tops of hills, the ocean, &c., it appeared that the
proportion of oxygen did not sensibly differ in them
all. The healthiness of certain airs, therefore,
must depend upon some other circumstances.
Although the great mass of the atmosphere is to
be considered as consisting of oxygen and hydro-
gen, yet it contains a small quantity of many other
gases, and also water, and a variety of exhalations
and substances dissolved in it. It always contains
a portion of carbonic acid gas, perhaps 1 part in
1000,for alkaUes become effervescent when exposed
to it, and lime water acquires a pellicle on being
HYDROGEN. 49
exposed a sufficient time to the action of the air,
even upon the highest mountains.
Since the oxygen of the atmosphere is continu-
ally abstracted from it by various decomposing
processes, it would appear that nature must have
some mode of renewing a principle so important.
Vegetables have been supposed to perform this
office, since they always exhale oxygen gas in the
day, and particularly when the sun shines. This
circumstance may be easily observed by putting
some leaves into an inverted tumbler of water
placed in the sun-shine. Minute globules of air
will be seen rising from the leaves, which, col-
lected at the top and examined, will be found to
be oxygen.
HYDROGEN.
Hydrogen is so called from two Greek words
signifying the genei^ator of water, because it is one
of the constituent principles of this fluid. It is
also one of the ingredients of bitumen, of oils, fat,
ardent spirits, ether, and of all the proximate com-
ponent parts of animal and vegetable bodies : it
forms a constituent part of all animal and vegeta-
ble acids : it is one of the elements of ammonia,
and of various compound gases.
It possesses so great an affinity for caloric, that
it is impossible to procure it in the concrete or
liquid state, independent of combination. Hydro-
gen united to caloric forms hydrogen gas.
Hydrogen gas is the lightest substance whose
weight we are able to to estimate; when in its
purest state it is about thirteen times lighter than
atmospheric air. It is unfit for respiration j ani-
VOL. II. E
50 HYDROGEN.
mals, when obliged to breathe in it, die ahnost in-
stantaneously. It has a peculiar and disagreeable
smell.
It is decomposed by living vegetables, and its
base is one of the constituents of oil, resin, &c.
It is highly inflammable, and burns rapidly when
kindled in contact with atmospheric air, or oxygen
gas, by means of the electric spark, or by an in-
flamed body, exhibiting a blue lambent flame.
Water absorbs about one thirteenth of its bulk.
It dissolves carbon, sulphur, phosphorus, arsenic,
and many other bodies. When its basis combines
with that of oxygen gas, water is formed, and with
nitrogen it forms ammonia.
An easy method of obtaining hydrogen gas
consists in subjecting water to the action of a
substance which is capable of decomposing this
fluid.
For this purpose, let sulphuric acid, diluted
with four or five times its weight of water, be
poured on iron filings or bits of zinc, in a small
retort or glass bottle ; as soon as the diluted acid
comes in contact with the metal, a violent effer-
vescence takes place, and hydrogen gas escapes,
without external heat being applied. It may be
collected in the usual manner over water, taking
care to let a certain portion escape, on account
of the common air contained in the disengaging
vessel.
Hydrogen gas is often found in great abundance
in mines and coal-pits, where it is sometimes gene-
rated, and becomes mixed with the atmospheric air
of these subterraneous cavities. If a lighted can-
dle be brought into this mixture, it explodes, and
produces the most dreadful effects. It is called by
miners the Jire damp. It generally forms a cloud
HYDROGEN. 51
in the upper part of the mine, on account of its
lio-htness, but does not mix there with atmospheric
air, unless some agitation takes place. The miners
frequently set fire to it with a candle, laying, at
the same time on their faces, to escape the violence
of 'the shock. An easier and safer method of
clearing the mine is, by leading a long tube
through the shaft of it to the ash-pit of a furnace ;
by this means the gas will be conducted to feed
the fire.
Hydrogen gas, though itself inflammable, extin-
guishes burning bodies, and is incapable of main-
taining combustion. Bring an inverted jar filled
with hydrogen gas over the flame of a candle, and
depress the jar, so that the lighted wick may be
wholly surrounded by the gas 5 the candle will be
immediately extinguished.
Hydrogen gas is only inflammable when in con-
tact with atmospheric air or oxygen gas. Fill a
small phial with hydrogen gas, and take it from
the pneumatic trough, placing the thumb on the
mouth thereof, to prevent the gas from escaping ;
if a lighted taper be applied to the mouth of the
phial, the gas will take fire, and burn with a lam-
bent flame. The gas will only burn where it is in
contact with the atmospheric air ; the flame will
descend gradually, till all the gas is consumed.
If the hydrogen gas be pure, the flame will be of
a blue colour ; but if the gas holds any substance
in solution, which is generally the case, the flame
is tinged of different colours, according to the sub-
stance. It is usually reddish, because the gas
holds in solution a little charcoal.
On this principle i? constructed the philosophical
candle, which cannot be easily blown out. Fill
with hydrogen gas a bell glass, furnished with a
E 2
52 HYDROGEy.
capillary tube ; compress the gas, by making the
bell descend below the surface of the water in the
pneumatic trough ; then apply a lighted taper to
the upper extremity of the tube ; the gas will take
fire, and exhibit a candle, which will burn till all
the gas is exhausted.
Artificial fire-works may be constructed by filling
bladders with hydrogen gas, and connecting them
with revolving jets, tubes, &c., bent in different
directions, and formed into various figures pierced
with holes of different sizes. The air which is
forced through these holes by pressing the blad-
ders, will, when inflamed, exhibit a curious fire-
work, without either noise or smoke.
By the inflammable property of hydrogen gas,
and the effects of electricity, a curious lamp has
been invented by Volta, which, by turning a stop
cock only, may instantly be lighted, and that many
hundred times.
Hydrogen gas burns more readily in proportion
as it is surrounded with a larger quantity of atmos-
pheric air. Hydrogen gas and atmospheric air, or,
what is better, oxygen gas, may be mixed together,
so that every particle of each gas shall be contigu-
ous to a particle of the other, in which case they
will burn with great rapidity.
Into a strong bottle, capable of holding about
four ounces of water, put one part of hydrogen
gas and two of amospheric air. On applying a
lighted taper, the mixture will explode with a loud
report, and the inside of the bottle will become
moist. It will be prudent to wrap a handkerchief
round the bottle, to prevent it from doing any in-
jury if it should burst.
The same experiment may be made with oxygen
gas, instead of atmospheric air, changing the pro-
HYDROGEN. 53
portions, and mixing only one part of oxygen gas
with two of hydrogen. The report will then be
much louder than with common air.
This experiment may be made conveniently by
means of an apparatus called the hiflammahle air pis-
tol. To charge it, nothing more is necessary than to
introduce its mouth inverted into a wide-mouthed
bottle, filled with a mixture of oxygen and hydro-
gen gas, leaving it in for a few seconds ; it is then
to be stopped with a cork, and may be fired by the
electrical spark taken from the prime conductor of
the machine, or by a charged Ley den phial.
It has been, with great plausibility, conjectured,
that the noise of thunder is the effect of the rapid
combustion of hydrogen and oxygen gas, fired by
the electric spark ; and that the rain which falls so
copiously at the time of thunder-storms, is owing
to a sudden formation of water by this means.
From its Hghtness, it has been employed for
making air-balloons, which have been already de-
scribed.
Soap-bubbles, filled with hydrogen gas, ascend
in the air. To show this, fill a bladder with hydro-
gen gas, and fasten it to a tobacco-pipe ; dip the
bowl of the pipe into a lather of soap, squeeze the
bladder gently, in order to form a bubble, and de-
tach it in the usual manner. These bubbles will
rise rapidly into the air : if a lighted taper be pre-
sented to them, they catch fire and burn with a
slight explosion.
If the bladder be filled with a mixture of hydro-
gen and common air, the soap-bubbles will ascend,
and when the taper is presented to them they will
explode with a loud report. This experiment is
more striking if oxygen gas be mixed with
hydrogen. If the bladder be squeezed so as to
E 3
S4i HYDROGEN AND OXYGEN.
form a great many bubbles on the surface of the
bason,'the report will be as loud as that of a cannon.
It has lately been discovered, that hydrogen, like
oxygen, is an acidiJi,:hig prmciple. United to chlo-
rine, it forms hydro -chloric acid, which is the same
as muriatic acid. Combined with iodine, it forms
hydriodic acid.
When hydrogen gas is united to sulphur, it
forms sulphureted hydrogen, which has also the
properties of an acid. Tellureted hydrogen has
also acid properties.
Hydrogen and Oxygen.
It has been already mentioned, that these two
elements, when combined, form "doater.
Till lately, water was considered as a simple sub-
stance, or element ; no one had ever been able to
decompose it ; and the decomposition of it, which
is daily effected in natural processes, had escaped
observation. We shall, however, give such evi-
dent proofs of the decomposition and recompo-
sition of water, as will clearly show that it is not a
simple body.
Ea:periment I. — A tube of common glass E F
(Plate 2. fig. 70j well annealed, and difficult to be
fused, about ten or eleven lines diameter, was
placed across a furnace C F E D, in a position
somewhat inclined ; and to its upper extremity was
adapted a glass retort A, containing a known quan-
tity of distilled water, and resting on a furnace
V V. To the lower extremity of the glass tube F
was applied a worm S S, connected with the dou-
ble-tubulated flask H, and to the other tubulure
was adapted a bent glass tube K K, destined to con-
vey the gas to an apparatus proper for determining
HYDROGEN AND OXYGEN. 55
the quality and quantity of it. When the whole
was thus arranged, a fire was kindled in the fur-
nace C F E D, and maintained in such a manner,
as to bring the glass tube E F to a red heat, but
without fiising it ; at the same time as much fire
was maintained in tlie furnace V V X X, as to
keep the water in the retort A in a continual state
of ebullition,
In p]'oportion as the water in the retort A as-
sumed the state of vapour by ebullition, it filled
the interior part of the tube E F, and expelled the
atmospheric air which was evacuated by the worm
S S, and the tube K K. The steam of the water
was afterwards condensed by cooling in the worm
S S, and fell drop by drop, in the state of water,
into the tubulated flask H. When the whole of
the water in the retort A was evaporated, and the
liquor in the vessels had been suffered to drain off
completely, there was found in the flask H a quan-
tity of water, exactly equal to that which was in
the retort A, and there had been no disengage-
ment of any gas ; so that this operation was merely
a common distillation, which gave absolutely the
same result as if the water had never been brought
to a state of incandescence, in passing through the
glass tube E F.
Ea:perime7it II. — Every thing being arranged as
in the preceding experiment, twenty-eight grains
of charcoal reduced to particles of a moderate size,
and which had been previously exposed for a long
time to a white heat in close vessels, were intro-
duced into the glass tube E F. The operation was
then conducted as before, and the water in the re-
tort A kept in a continual state of ebullition, till it
was totally evaporated.
The water in the retort A was distilled as in the
E 4-
56 HYDROGEN AND OXYGEN.
preceding experiment, and being condensed in the
worm S S, had fallen drop by drop into the flask
H ; but at the same time there had been disen-
gaged a considerable quantity of gas, which escaped
through the tube K K, and was collected in a pro-
per apparatus. When the operation was finished,
there was found nothing in the tube E F but a few
ashes, and the twenty-eight grains of charcoal had
totally disappeared.
The gases disengaged were found to weigh alto-
gether 113.7 grains. There were found two dif-
ferent kinds of gas, viz. 114 cubic inches of
carbonic acid gas, weighing 100 grains, and 380
cubic inches of a very light gas, weighing 13.7
grains. This last gas took fire, on being applied
to a lighted body in contact with the air. In ex-
amining afterwards the weight of the water whicli
had passed into the flask, it was found less than
that in the retort A by 85.7 grains. In this ex-
periment, therefore, 85.7 grains of water and 28
grains of cliarcoal formed carbonic acid gas equal
to 100 grains, and a peculiar gas susceptible of in-
flammation, equal to 13.7 grains. To form 100
grains of carbonic acid gas, 72 grains of oxygen
must be united to 28 grains of charcoal or carbon.
The 28 grains of charcoal put into the glass-tube
EF, took, therefore, from the water, 72 grains of
oxygen, since there was formed carbonic acid equal
to 100 grains. It appears, then, that 85-7 grains
of water are composed of 72 grains of oxygen, and
13.7 grains of a substance forming the base of a
gas susceptible of inflammation. The following is
a proof of it.
The apparatus being arranged as above, instead
of the 28 grains of charcoal, 274^ grains of thin
-shavings of iron, rolled up in a spiral form, were
HYDROGEN AND OXYGEN. 57
introduced into the tube E F ; the tube was then
brought to a red heat as before ; and, in the same
manner, the whole of the water in the retort A was
made to evaporate.
In this experiment there was disengaged only
one kind of gas, which was inflammable ; there was
obtained of it about 406 cubic inches, weighing 15
grains.
The 274 grains of iron put into the tube E F
were found to weigh 85 grains above what they did
when introduced ; and the water first employed
was diminished 100 grains.
The volume of these iron shavings was found to
be greatly enlarged. The iron was scarcely any
longer susceptible of attraction by the magnet ; it
dissolved without effervescence in acids ; in a word,
it was in the state of a black oxyd, like that which
has been burned in oxygen gas.
In this experiment there was a real oxydation
of the iron by the water, entirely similar to that
effected in the air by the aid of heat. 100 grains
of water were decomposed ; and of these 100
grains, 85 united to the iron, to reduce it to the
state of black oxyd ; these 85 grains, therefore,
consisted of oxygen ; the remaining 15 grains,
combined with caloric, formed inflammable gas.
It thence follows, that water is composed of oxygen
and the base inflammable gas, in the proportion of
85 to 15, or of I7 to 3.
If it be true, as we have endeavoured to prove,
that water is composed of hydrogen combined with
oxygen, it thence results, that, by re-uniting these
principles, water ought to be produced. This, in-
deed, is what takes place when, into a vessel filled
with oxygen, a stream of hydrogen is introduced
and set fire to.
58 HYDROGEN AND OXYGEN.
In proportion as the combustion proceeds, water is
deposited in the internal surface of the vessel ; the
quantity of this water gradually increases, and it
unites itself intolarge drops, which run down the sides
of the vessel, and are collected in the bottom of it.
In making this experiment, proper means were
taken to ascertain the weight of the gases em-
ployed. Before the experiment, the vessel v/as
weighed ; and, by weighing it after the operation,
the weight of the water that had been formed was
obtained. Here, then, is a double proof; on the
one hand, the weight of each of the gases em-
ployed ; and, on the other, the weight of the water
formed ; and these two quantities were found to
be equal within a two hundredth part. It was thus
found that 85 parts by weight of oxygen, and 15
parts also by weight of hydrogen, are required to
compose 100 parts of water.
These phenomena of the decomposition and
recomposition of water are continually effected be-
fore our eyes, by the temperature of the atmos-
phere, and the agency of compound affinities. It
is this decomposition which gives rise, at least in a
certain degree, to the phenomena of spirituous fer-
mentation, to those of putrefaction, and to those
of vegetation.
Pure water is perfectly transparent, and has no
taste nor smell. It is not liable to change. It can
absorb a variety of gases ; and when exposed to
the atmosphere, it always contains a small quantity
of common air, which may be separated by boiling,
or by the air-pump. Rain-water is the purest which
we see in nature ; but, for delicate chemical pro-
cesses, it is distilled in glass vessels. Spring- water
generally holds some salts in solution, which gives
it various properties.
HYDROGEN AND CARBON. 59
Hydrogen gas combines with several simple
bodies, constituting, with them, peculiar and dis-
tinct gases.
Hydrogen and Carbon.
Hydrogen gas unites to carbon, and forms, with
it, HydrO'Carhonate gas. Of this there are two
kinds, according to the quantity of carbon which
they contain.
Light Hyd?^o-Carbo?iate. — This is frequently
seen rising from stagnant ponds, when stirred. It
may also be procured by passing the vapour of
water over red hot charcoal. It burns with a pale
blue flame. It is also called Light carbureted Hy-
drogen. It is contained very abundantly in
many coal mines, where it is disengaged from
fissures in the strata, often in great quantities;
which are called by the miners blowers. When it
has accumulated iu any part of the mine, it forms
an explosive compound, by its admixture with the
common air : and when the miners approach it with
lighted candles or lamps, it inflames with a tre-
mendous explosion, killing the workmen and de-
stroying the works. Indeed, nothing can be more
terrible than such accidents ; and there is reason
to think that they have happened more frequently
than is generally known. The body of miners are,
therefore, infinitely indebted to Sir Humphry
Davy for his invention of the Safety-lamp, an in-
strument which they can carry lighted into an ex-
plosive mixture, without any danger of setting fire
to it. This gas is called the Fire-damp by the
miners.
Bi'Carbureted Hydrogen. ■ — This gas contains
60 GAS ILLUMINATION.
twice as much carbon as the last. It is heavier
than it, and is also called the Heavy hydro-car-
bonate. It burns with a bright white flame, like
that of the best wax candles. It has been called
the olejiant gas, because, when mixed with chlo-
rine in an exhausted vessel, or over water, a pe-
culiar fluid was formed, resembling a thick oil, but
which has been termed by Dr. Thomson, Chloric
ether.
Bi-carbureted hydrogen may be procured by
heating, in a retort, four parts of sulphuric and
of one alkohol ; when the mixture boils the gas
comes over.
Gas Illumination. — The carbureted hydrogen
gases are now extensively employed for the pur-
pose of giving light. When coal is put into an
iron retort placed in a furnace, an inflammable gas
is given out, which is a mixture of the two above-
mentioned species of hydro-carbonate, together
with small quantities of carbonic acid gas, car-
bonic oxide, sulphureted hydrogen, tar, ammonia,
and water. These last substances are separated
by passing the gas through a mixture of quicklime
and water; and the purified gas then passes into
the gasometer^ from which it is distributed by
means of pipes. The coal that has been thus acted
upon, being deprived of its volatile principle, is con-
verted into colce.
The kind of coal, fittest for the production of
good gas, is that which contains most bitumen and
least sulphur.
Messrs. J. and P. Taylor have lately taken out a
patent for the production of carbureted hydrogen
gas from oil. The oil is decomposed by suffering
it to drop into a bent iron tube, laid through a
furnace. The oil is separated into charcoal and
SULPHURETED HYDROGEN GAS. 6l
bi-carbureted hydrogen, the flame of which much
exceeds in whiteness and brilliancy that of coal
o-as, which is a mixture of the two species of hydro-
carbonates. Another material advantage in the use
of the oil gas is, that it is not mixed with the impu-
rities of coal gas, many of which are highly inju-
rious to health, and to the furniture of houses.
From experiments it appears that the coal gas does
not contain above 10 per cent, of bi-carbureted
hydrogen ; while the oil gas consists almost entirely
of it.
Sidphiir^efed Hydrogen Gas.
This is a combination of hydrogen gas with sul-
phur. It has an extremely fetid odour. It is in-
flammable. It cannot support life nor combustion :
indeed, it is highly deleterious. Water can absorb
it, and acquires its peculiar smell. The mineral
waters of Harrowgate and Aix-la-Chapelle owe
their properties chiefly to this gas.
Sulphureted hydrogen gas has the property of
causing metallic oxides to re-approach the metallic
state ; the hydrogen of the gas attracting the oxy-
gen. If a piece of paper, dipped in a solution of
acetite of lead, be exposed to this gas, it instantly
becomes blackened. If letters be written with the
solution of lead, they will be invisible when dry,
but will become black on exposing them to sul-
phureted hydrogen.
It has also acid properties. It unites with the
alkalis and the earths, forming compounds called
Hydro-sul'phurets.
This gas affords an exception to the doctrine of
Lavoisier, that oxygen was the only acidifying prin-
ciple ; for in it there is no oxygen, yet it performs
62 PHOSPHORATED HYDROGEN GAS.
the most important functions of an acid, reddening
vegetable blues, and combining with alkalis. The
hydro-sulphurets are formed by passing a stream of
this gas through solutions of the alkalis.
Phosphorated Hydrogen Gas,
This gas consists of hydrogen and phosphorus.
It is so combustible that it inflames by mere con-
tact of atmospheric air. It has a very disagreeable
smell, like that of putrid fish.
To procure it artificially, put one part of phos-
phorus and ten of a concentrated solution of potass,
into a glass retort, and apply a gentle heat. When
the mixture boils, the gas will come over, and may
be collected in the pneumatic apparatus.
In preparing this gas, the body of the retort
should be filled as nearly as possible with the mix-
ture, otherwise the first portion of the gas, finding
atmospheric air in the retort, inflames, a vacuum
is produced, and the water is forced up into the
retort, endangering the bursting of it.
If the bubbles of air which are formed in the
retort are suffered to escape into the atmosphere,
they will inflame instantly with a slight explosion;
at the same time a beautiful dense white circular
ring of smoke rises, and gradually enlarges as it
ascends.
This gas maybe made to burn under the surface
of water. Put into a deep glass some phosphuret
of lime, and half the quantity of oxy-muriate of
potass : fill the vessel with water. Procure a long-
necked glass funnel and plunge it into the vessel,
putting it down to the bottom. Take some con-
CHLORINE. 63
centrated sulphuric acid and pour into the funnel.
As soon as the decomposition of the water and that
of the muriate takes place, flashes of fire will be
seen to issue from the bottom of the vessel, having
a screen colour.
If a ribbon be impregnated by a solution of gold,
and hung in a jar containing this gas, the gold will
be revived, and will gild the ribbon.
CHLORINE.
This gaseous body is now generally regarded as
an elementary substance : but it was lately con-
sidered as a combination of muriatic acid with oxy-
gen, and was hence called oxygenated muriatic
acid gas.
It is obtained by heating a mixture of muriatic
acid and black oxide of manganese over a lamp :
the chlorine will be evolved. In this process, ac-
cording to the present theory respecting the ele-
mentary nature of chlorine, the oxide of manganese
and muriatic acid decompose each other : the oxy-
gen of the oxide unites to the hydrogen of the
muriatic acid to form water, leaving the other
constituent of the acid, viz. the chlorine, disen-
gaged.
Chlorine is rapidly dissolved by water, the so-
lution being of a pale yellow colour : it has a
nauseous taste, and an extremely suffocating smell.
When the gas is perfectly free from moisture, it
has no action on vegetable colours, but, dissolved
in water, it destroys them entirely.
From this property, it is extensively employed in
shortening the process of bleaching linen, and
also paper; but it is said that it is apt to injure
64 CHLORINE.
the durability of the substances bleached, and no
doubt, except due care is employed, this must be
the case. Prints that have been stained by smoke
and dust may also be whitened by it, as it does not
act upon the printing ink.
Chlorine has likewise been found extremely effi-
cacious in destroying the putrid effluviag in pri-
sons, and hospitals, and preventing the infection
of the small-pox. But when used for this purpose,
a small quantity only is diffused through the air,
for, when taken into the lungs by itself, it is fatal
to animal life ; and, indeed, in preparing it, great
precaution should be used not to inhale it, as it is
extremely dangerous if not sufficiently diluted.
Notwithstanding its unfitness for respiration, it
supports combustion in a remarkable degree.
Some bodies, as phosphorus, and several of the
metals, are spontaneously ignited when plunged
into a vessel of chlorine ; on this account it is now
reckoned one of the supporters of combustion, a
property which was lately supposed to be only en-
joyed by oxygen. In this view, combustion is re-
garded only as the result of intense chemical
action, and it is supposed that the compounds of
chlorine have less capacity for caloric than their
constituent principles, and, consequently, that ca-
loric is evolved at the moment of their formation.
Chlorine is known to combine with oxygen in
three different proportions, forming
1. Omde of Chlorine, or Euchloriney a gaseous
body, not acid, having a smell less irritating than
chlorine.
2. Ojnjchloric Acid, which does not exist inde-
pendent of water or a base.
3. Chloric Acid. — Chloric acid cannot be ob-
tained unmixed with water. It is colourless and
CHLORINE. C)5
sour ; acts on metals, and combines with alkalies,
forming chlorates.
Chlorate of potash was formerly called oxymu-
riat of potash. It is a soluble white salt. When
heated it gives out oxygen, and the residue is
chloride of potassium. It forms extremely explo-
sive compounds with phosphorus, sulphur, and
charcoal. A grain, with a minute portion of phos-
phorus, laid upon an anvil, and struck with a
hammer, makes a very loud report ; but this
experiment should not be attempted by the i/owig
student. From its detonating quahty, it had been
imagined that it could be used advantageously in
the manufacture of gunpowder, but it has not
succeeded.
Chlorate of potash is made by causing a stream
of chlorine to go through a solution of caustic
potash.
The combinations of chlorine with other simple
bodies, form chlorides, if they are not acids, as
chloride of sulphur, &c.
Chlorine and hydrogen. This compound body,
which, according to the present nomenclature, is
called hydrochloric acid gas, was known by the
name of muriatic acid gas. It is readily obtained
by distilling a mixture of common sea salt and sul-
phuric acid. The sulphuric acid combines with the
soda, one of the constituents of salt ; and the other
constituent, the muriatic acid gas, is set free. Mu-
riatic acid gas cannot support life nor combustion.
It has a «harp pungent odour, and occasions white
fumes when it is mixed with moist atmospheric air.
It reddens vegetable blues. It combines with the
alkaline bases : with ammoniacal gas it forms mu-
riate of ammonia.
VOL. II. F
60 IODINE.
It is decomposed by the electric spark into hy-
drogen and chlorine.
It is readily absorbed by water, which then
becomes very acid, and forms the liquid muriatic
acid.
The muriatic acid, called also the mai^ine acid
and the spirit of salt, is in very common use. It is
obtained, as above-mentioned, by distilling sea salt
and sulphuric acid. It exists in a state of combin-
ation with alkalies and earths in the mineral
kingdom in great quantity, chiefly with soda, lime,
and magnesia. With soda it forms muriate of soda,
common or sea salt, with which every part of the
ocean is impregnated, and also some lakes. Mu-
riate of soda also exists in the form of a rock in the
earth, whence it is extracted : it is called rock salt.
The most considerable mines of rock salt are in
Poland ; extensive mines are also worked in Hun-
gary, Spain, and Cheshire in England. Muriate
of soda is obtained also from the sea water, by
driving off the water by evaporation ; and this is
done either by exposing salt water in shallow places,
called saltpans, to be evaporated by the heat of the
sun, or by boiling salt water in vessels, or by these
methods combined. Muriate of soda, so procured,
is always contaminated with muriate of magnesia
and muriate of lime, from which the salt is puri-
fied by different processes.
IODINE.
This substance, considered as a simple body, has
been but lately discovered. It exists in certain
marine plants, and is procured from kelp, which is
SULPHUR. ()7
made by burning them. It is obtained first in
the form of fumes, of a violet color, which con-
dense in small opaque crystals of a blackish grey
color and metallic lustre, resembling plumbago. It
appears to be an element that exists in small quan-
tity. It is capable of producing acids by combin-
ation with other substances. With oxygen, it
forms iodic acid ; and, with hydrogen, it forms hy-
driodic acid. It combines with phosphorus at the
common temperature, giving out heat and light,
and produces with it phosphuret of iodine. With
sulphur, it makes sulphur et of iodine.
Iodine, also, unites with all the metals, forming
with them iodurets.
SULPHUR.
Sulphur, known also by the name of brimstone^
is a mineral substance, frequently found pure in
nature.
It is of a pale yellow colour, without taste and,
also without smell, except when heated. It is
chiefly a volcanic product, and a great deal of what
is used in this country is brought from Italy and
Sicily. It is found also in nature combined with
most of the metals as ores : united to iron, it forms
iron pyrites.
Sulphur is extracted from pyrites by exposing it
to heat in tubes, by which the sulphur is driven out
and received in vessels with water : when melted
and poured into moulds, it constitutes the roll sul-
phur in common use. A good deal of this is made
in England. The sulphur thus obtained, however,
is not quite pure. To purify it, it is sublimed by
F ^
(j8 sulphur.
a gentle heat in close rooms, and thus forms Jloxvei^s
oj' sulphur.
If sulphur be exposed to heat it will soon fuse,
and, by continuing the fusion for some time, it will
become thick and tenacious. If worked between
the fingers under water in this state, it acquires a
consistency like wax, and may be employed for
taking impressions from seals or gems. This
change in the sulphur has been ascribed to oocijda-
tion; but the same effect takes place if the sulphur
be kept in fusion without access of air.
Sulphur becomes electric by friction, and then
exhibits negative electricity. It is soluble in oils.
It does not combine with charcoal, but unites to
phosphorus by means of heat. Sulphur and iron
have a great attraction for each other. If a bar of
iron be heated to whiteness, and then touched with
a roll of sulphur, the two bodies combine and drop
down together in a fluid state, forming sulphuret of
iron. Sulphur also unites to potash and to soda, by
melting them together in a crucible : by this liver-
brown substances are formed, called sulphurets of
potash or of sodciy which are soluble in water.
Sulphur is a highly inflammable body, burning
with a pale blue flame. Put some threads, dipped
in sulphur, into a vessel floating in water. Set
fire to them, and cover the whole with an inverted
glass. The threads will continue to burn for some
time, and the receiver will be filled with a dense
white vapour. This vapour is the sulphurous acid,
formed by the union of the sulphur and the oxy-
gen during the combustion. It is absorbed by
the water which will ascend in the receiver.
Let the whole then be left till the vessel is be-
come again transparent. If the water be exam-
9
SULPHURIC ACID. Qg
ined, it will have a suftbcating odour and an acid
taste.
Sulphurous acid, or the vapour of burning sul-
phur, has been found very useful for destroying
the infection of clothes and small uninhabited
places, and for fumigating letters from contagious
places. It is used in dyeing, and for whitening
straw and silk.
Sulphuric Acid.
This acid is composed of sulphur and oxygen,
and contains a greater proportion of oxygen than
sulphurous acid.
This acid is the same with that commonly known
by the name oi Oil of Vitriol. It was so called ori-
ginally, because it was procured from green vitriol;
now called sulphate of iron.
Common oil of vitriol has strong acid properties.
It is of an oily consistence, and has usually a brown
tinge, from impurities. It is inodorous, and about
twice as heavy as water. It is highly corrosive,
acting strongly on vegetable and animal substances.
It attracts water very strongly, and cannot be
entirely separated from it by any known process.
When exposed to the air, it attracts the watery
vapour in the atmosphere, so as to increase I'apidly
in weight, which will be doubled in a month. If
mixed with cold water, it suddenly becomes ex-
tremely hot, even more so than boiling water; and
on this account, when it is necessary to dilute it
with water, this should be performed very gradually.
Sulphuric acid is now made by burning sulphur
mixed with nitre, in close chambers, entirely lined
F 3
70 CARBON.
with lead, on the floor of which a thin layer of
water is put. The combustion of the nitre fur-
nishes oxygen to the sulphur, and the sulphuric
acid is condensed in the water. It is in this manner
that the common oil of vitriol is made: but it then
contains many impurities ; when freed from these,
it is colourless.
If sulphuric acid be heated in contact with a
combustible body, as charcoal or mercury, it loses
part of its oxygen, and is then converted into sulphu-
reous acid gas, which must be collected over mer-
curv, as it is absorbable by water.
CARBON.
This elementary body is widely diffused through-
out nature. Common charcoal consists of it, mixed
with a small quantity of foreign matter. The
purest variety of charcoal is lamp black.
Carbon exists as a constituent principle in all
vegetable and animal matters, and remains fixed,
after all the volatile parts have been carried off,
during the process of combustion.
Charcoal is very nearly the same, from whatever
it has been procured. It is always black and brittle,
and exhibits the fibrous structure of the wood. It is
not at all liable to change, and hence wood is some-
times charred on the outside, when driven into the
ground for piles, and similar uses.
The diamond, a substance so very dift'erent in
appearance, has been found by experiment to be
only crystallized carbon. Diamonds are found only
in Asia and Brazil, and always in the alluvial soil.
Diamond is the hardest body, and can only be cut
CARBON AND OXYGEN. 71
by its own powder. When found in the earth,
they are crystalHzed, but are usually rough,
having lost the angles of their crystals by attrition.
They may be cleaved or split, and are then cut
with facets for jewellery. They are of various
colours. The diamond was long thought to be an
incombustible body, but it is now known to be
capable of being burnt ; and by its union with oxy-
gen, it forms carbonic acid. But although we know
that diamond is only carbon, no attempts to crys-
tallize carbon, and thus to make diamonds, have
succeeded. Art cannot always imitate the pro-
cesses of nature, even when the materials she has
used are known.
Carbon and Oxygen.
Carbon unites to oxygen in two proportions. We
shall first consider the most common one :
Carbonic Acid. — If charcoal be burnt, it com-
bines with the oxygen of the atmosphere, and
thus forms an acid, which, however, cannot be
condensed into the liquid form, but is always
aerial. Carbonic acid exists in great abundance
in nature, combined with mineral bodies, chiefly
lime. All limestones are formed of carbonic acid
in a fixed state, united to lime. Hence this gas
was at first called jixed air, which name is still
sometimes used.
It may be procured from limestone or marble,
in the following manner : put a quantity of broken
pieces of marble or chalk into a retort, and add to
it some sulphuric acid, diluted with six times its
weight of water: a brisk effervescence will ensuei,
F 4
7^ CARBONIC ACID.
and the carbonic acid gas will be disengaged, and
maybe collected in the pneumatic apparatus. In this
process the sulphuric acid severs the lime, leaving
the carbonic acid free, which escapes in the gase-
ous form.
Carbonic acid gas cannot support flame, as may-
be seen by plunging a lighted taper into a vessel
of it : it will be instantly extinguished.
It is fatal to animal life : a small animal confined
in it would die in a few minutes.
Its taste is sour: and it is capable of being ab-
sorbed by water. Water so impregnated has an
acidulous taste, and reddens vegetable blues.
Many mineral waters owe their qualities to this gas,
which is contained in them, and they may be imi-
tated by impregnating water with carbonic acid gas.
Agitation and pressure promotes the absoi'ption ;
and in this manner the artificial soda water is
made.
During the process of fermentation, this gas
is disengaged, and yeast is carbonic acid enveloped
in a viscous substance. If a lighted candle be
plunged into the upper part of a cask containing
fermenting liquor, it will be extinguished, the
apparently empty part of the vessel being filled
with carbonic acid gas.
This gas is heavier than common air; hence,
when disengaged, it occupies the lowest situation.
It may be poured from one vessel into another,
which makes a pretty experiment. Fill a vessel
with this gas, and then, having placed a bit of
lighted paper in the bottom of an empty tumbler,
pour the gas into the tumbler upon the taper: the
flame will be extinguished : here the gas will be
invisible, but its presence is thus manifested.
CARBONIC OXIDE.- 7^
This gas is often found in the lower part of
caverns, wells, mines, and other subterranean
places. In mines it proves frequently fatal to the
miners, who call it the choke damp. Wells, or
similar places, which have been shut up for a long
time, should never be entered without first putting
down a lighted candle : if this is extinguished, it
is not safe to go down. There are some caverns
in which this gas is produced in so great a quantity,
that it runs out at the opening, like a stream of
water: this is particularly the case with the cele-
brated Grotto del Cane. A dog is suffocated
if it be held for a short time in the lower part
of the cavern, but the upper part is free from
this gas.
Charcoal should never be burnt in rooms that
have no chimney, because the red hot charcoal
unites with the oxygen of the atmosphere, and
forms carbonic acid, which cannot escape. Some
melancholy accidents have happened from this
cause. This gas has also been called mephitic air,
from its suffocating quality.
Carbonic acid combines with all the alkalies, and
with the alkaline earths, lime, magnesia, barytes,
and strontia. With these it forms a class of salts,
called carbo7iates.
Carbon does not combine with any of the metals
except iron. This combination is the carburet of
iroiiy called also plumbago and black lead ; which,
however, contains only five per cent, of iron.
It is the substance used for making black lead
pencils.
Carbonic Oiide. — This body is always gaseous.
It contains only half as much oxygen as carbonic
acid does. It is void of taste and smell, and
fatal to animal life. It is inflammable, burning
74 CARBON AND NITROGEN.
with a blue lambent flame, but does not explode
when mixed with atmospheric air. It is pro-
cured by depriving carbonic acid of part of its
oxygen. This is effected by exposing equal parts
of chalk and filings of zinc to a gradual red heat,
suftering the first product to escape, which is car-
bonic acid gas. The zinc deprives the carbonic
acid in the chalk of part of its oxygen.
Carbon and Nitrogen.
This combination is called cyanogen. It is a gas-
eous body, having a penetrating and peculiar
smell, and burning with a purple flame. It red-
dens vegetable blues.
When cyanogen combines with hydrogen, it
forms a triple compound, called hydrocyanic acid :
this is also called Prussic acid. Prussic acid is a
liquid having a very pungent odour, like that of
bitter almonds. It is extremely acrid, and highly
poisonous. It is called Prussic acid, because it
forms one of the constituents of the well-known
pigment Prussian blue, which is a combination of
hydrocyanate of iron with alumine.
PHOSPHORUS.
This highly inflammable substance is not met
with in nature uncombined ; but it exists combined
with oxygen, forming phosphoric acid, in many
animal and mineral substances.
Phosphorus is a yellowish semi-transparent mat-
ter of the consistence of wax. It is luminous in
PHOSPHORUS. 75
the dark at the common temperature of the atmo-
sphere.
To show this property in a striking manner,
write with a stick of it upon black or purple paper,
or any other smooth surface ; the writing will be
luminous as if on fire. The fiery appearance dis-
appears and appears again by blowing upon it. It
is necessary, in making this experiment, to cut the
phosphorus under water, and to put it into a quill,
in order to defend the hands, lest it should take
fire 5 and great care ought to be taken lest any
particle should be left under the nails, or in any
other place, for if this were afterwards to take fire
it might occasion very serious accidents, as a burn
by it is extremely severe.
Very slight friction is sufficient to inflame phos-
phorus. Put a grain of it into brown paper and
rub it with some hard body, and it will take fire
and inflame the paper. It takes fire spontaneously,
and burns rapidly in the open air at 122° Fahr.,
with a brilliant flame. On this account, it is alwavs
kept under water ; and it should never be suffered
to lie exposed to the air.
Phosphorus is obtained by decomposing the
phosphoric acid by means of charcoal in a retort.
The oxygen of the acid unites to the carbon, form-
ing carbonic acid j and the phosphorus distils over
into water. The phosphoric acid is obtained by
decomposing calcined bones by sulphuric acid.
Bones consist chiefly of phosphate of lime j and
in this process the sulphuric acid joins to the lime,
leaving the phosphoric acid free.
Phosphorus is soluble in oil in small quantity,
which is thus rendered luminous. Sulphuric and
nitric ether, and ardent spirit, dissolve it, though
sparingly, in the cold.
70
Phosphorus and Oxygen*
Phosphorus unites with oxygen in two proper*
tions, forming phosphorous acid, which contains the
lowest proportion of oxygen ; and phosphoric acid,
which contains the greatest proportion.
Phosphoric acid may be made by the rapid com-
bustion of phosphorus in oxygen j but it is usually
obtained from calcined bones, by decomposing
them with sulphuric acid.
Phosphorus has the property of de-oxidizing se-
veral metallic solutions, as those of gold, silver,
copper, mercury, lead, tin. If a stick of phospho-
rus be left in a concentrated solution of nitrate of
copper, the copper wall be precipitated upon the
phosphorus in a metallic state.
It also combines with lime, forming phosphu-
ret of lime. When pieces of phosphuret of lime
are dropt into water, flashes of fire are seen
to rise out of the water, which is occasioned
by the phosphuret decomposing the water, and
part of the phosphorus uniting to the hydrogen
gas, forming phosphuretted hydrogen gas, de-
scribed before.
The phosphurets of barytes and strontia have
similar properties.
J^hosphorus combines with chlorine and with io-
dine j and also with sulphur and the metals. Its
union with hydrogen has been already noticed as
phosphuretted hydrogen gas.
BORAX.
This elementary substance is known only in
the boracic acid, which consists of it united to
oxygen.
FLUORINE. 77
Boracic acid is rarely found native, but is gener-
ally procured from the salt called borax.
Borax is boracic acid united to soda, or a borate
of soda. This is the //7zc«/ brought from Asia puri-
fied. It is found at the bottom of certain lakes in
Thibet, and in China. The boracic acid has been
decomposed but lately, when it yielded to the ap-
plication of galvanic electricity by Sir H. Davy.
Borax is in the form of a powder of an olive colour.
It is combustible.
Borax is much used as a flux in soldering metals,
and also for such stones as cannot be brought into
fusion by alkalies.
FLUORINE.
This name has been given, provisionally, to the
supposed base of the fluoric acid, which is ima-
gined to consist of fluorine and hydrogen.
The Jliwric acid has hitherto resisted all the en-
deavours that have been made to decompose it
completely ; and its real nature, therefore, con-
tinues uncertain. According to the present no-
menclature, it is now sometimes called hi/dro-
Jluoric acid.
Fluoric acid is obtained by adding sulphuric
acid to some pounded pure fluor spar, and ap-
plying heat.
Fluor spar is that mineral well known by the
name of Derbyshire spar, because very abundant
in that county. It is employed for making vases
and other ornamental works. It consists of fluoric
acid and lime, or, perhaps, calcium, the metal of
lime, and is hence called also fiuat of lime. The
sulphuric acid, having a stronger attraction for lime
78 ALKALIES.
than fluoric acid has, expels the latter and unites
itself to the lime.
It appears, that before the researches of Gay
Lusac and Thenard, the pure fluoric acid had ne-
ver been procured ; what had been considered as
fluoric acid, being, in fact, a different acid, the
siliceo-Jluorie acid. In their experiments, the leaden
receiver was cooled by ice, and the fluoric acid
condensed into a liquid form. In this state it is
the most caustic substance known, corroding the
skin instantly, and causing dangerous sores.
Fluoric acid combines with silica, and becomes
with it a permanent acid gas, called the siUceo-fiu-
oric acid. This was formerly called Jluoric acid
gas. It has a pungent irritating odour, will not
support combustion, and forms white vapours when
it comes in contact with the air. It corrodes glass,
and combines rapidly with water, forming the li-
quid siliceo-fluoric acid. This acid, formerly called
the Jiuoric, also acts on glass, and is very acid and
corrosive. In the process for making it from
fluor spar and sulphuric acid, a little silicious mat-
ter generally existed in the spar, or glass vessels,
that had been used ; and thus the siliceo-fluoric, and
not the fluoric acid, had been obtained.
Fluoric acid forms Jluates with the alkalies and
salifiable earths.
It also unites to borax, forming an acid called
the Jluo-boric acid. This does not act on glass,
and is not so corrosive as fluoric acid. It gives rise
to JiuO'borates.
ALKALIES.
Alkalies are an important class of bodies. They
have received this name because one of them,
POTASH. JO
soda^ was procured in great abundance from a
plant called kali, by the Arabians.
Alkalies have peculiar properties. They change
blue vegetable colours to green, and yellow to
reddish brown. They unite to oil and fat, forming
soap J thus rendering them miscible with water.
They have an acrid and peculiar taste. They are
caustic, or act powerfully upon animal substances.
They combine with acids, forming with them a
peculiar class of salts in which the properties of
the acid and alkali disappear.
Until lately, only three alkalies were known,
potash, soda, and ammonia. The two former
were called the fixed, the latter the volatile alkali.
Their number is now increased by the addition of
lithia.
POTASH.
Potash had long been* known by the name of
the vegetable alkali.
It is procured from the ashes of burnt vegetables
in the following manner. Dried vegetables are
burned in heaps ; the ashes are collected and lix-
iviated with water. Thus the potash in the ashes
is dissolved, while the rest of the ashes is insoluble.
The solution is poured off from the sediment, and
evaporated : what remains is the potash of com-
merce, which is of a grayish colour, and contains
some impurities: these are separated by being
heated in a furnace. It is then white, and is
called pearlash.
All xvood ashes have in them more or less of this
alkali, and hence they are applied to the same
purposes as potash, or pearlash.
so POTASH.
Potash and pearlash procured in this manner are
combined with a certain proportion of carbonic
acid, but not so much as to destroy completely its
alkaline properties : hence it is a sub-car bonate of
potash. To free the alkali from the carbonic acid,
another process is necessary. Twice its weight
of quicklime is added to the pearlash, and the
whole mixed with water. The carbonic acid
having a stronger affinity to the lime than to the
alkali, quits the latter, and forms carbonate of
lime, which, being insoluble, falls down, while the
purer alkali is kept in solution by the water, and
is afterwards separated by evaporation. Sometimes
it is still farther purified, if necessary, by mixing
the whole with alkohol, which dissolves the pure
alkali alone. The alkoholic solution ascends
to the top of the fluid, and is drawn off by decant-
ation.
Potash, when thus prepared, is a solid white
substance, and is called caustic potash, from its
property of corroding the skin and flesh when it is
applied to it : on this account it is frequently em-
ployed by surgeons.
Caustic potash, when prepared by alkohol, is
united to a portion of water, and is therefore a
hydrate of potash. It may be obtained free from
water by another process.
Potash may be made to combine with a greater
proportion of carbonic acid than in the state of
sub-carbonate, by causing a stream of carbonic
acid gas to pass through a solution of the latter
salt : when this solution is then evaporated, it af-
fords crystals of bi-carbonate of potash. This salt
is milder than the subcarbonate, and its crystals
are not deliquescent.
POTASH. 81
Tlie fixed alkalies were, until lately, regarded as
simple bodies, and one of the most brilliant disco-
veries of modern chemistry has been that which
showed them to be the oxides of peculiar metals.
The decomposition of the alkalies was effected
by means of voltaic electricity. By acting upon a
very small piece of caustic potash, the metallic base
was liberated, and proved to be solid, malleable, and
having a high metallic lustre resembling mercury.
This new metal is called potassium. It differs
considerably in its properties from all the metals
previously known. It is lighter than water, and
has so strong an attraction for oxygen, that it almost
instantly attracts it from the atmosphere and re-
turns to the state of oxide. If thrown into water,
it produces a very singular phenomenon ; it decom-
poses the water so rapidly that an explosion takes
place, accompanied by a flame. The same effect is
seen if a globule of the metal is placed upon a
piece of ice. This metal can only be preserved by
keeping it under naphtha, a liquid that does not
contain oxygen as one of its constituents.
Potash combines with all the acids forming neu-
tral salts.
Nitrate of potash, called also nitre, or saltpetre,
is produced in considerable quantities naturally,
particularly in Egypt. It has also been produced
artificially by making beds of animal and vegetable
substances, mixed with calcareous and other earths.
In process of time, an efflorescence of nitrate of
potash appears, and is separated by lixiviation. By
the decomposition of these substances, nitrogen
is disengaged, which, uniting to the oxygen of the
atmosphere, forms nitric acid ; and this uniting to
the alkali furnished by the vegetables and soil, pro-
duces the nitre. Nitrate of potash has the property
VOL. II. G
8g SODA.
of detonating when inflamed witli charcoal or
other easily inflammable bodies.
It is upon this property tlmt gunpowder is formed,
which consists of five partsof nitrate of potash, one
of charcoal, and one of sulphur. Chlorate of potash
is formed by passing chlorine gas through a solu-
tion of caustic potash. It is also called oxy-mu-
riate of potash. This salt detonates violently when
three parts of it mixed with one of sulphur are tri-
turated in a mortar, or struck on an anvil. With
phosphorus the effect is still greater. It makes a
powerful gunpowder when employed as an ingre-
dient.
If a small quantity of it be mixed with some
sugar, and sulphuric acid be added, a sudden and
vehement inflammation will be produced. These
experiments require great caution.
SODA.
This has also been called the fossil or mineral
alkali, because supposed peculiar to the mineral
kingdom. It is obtained chiefly from the ashes of
marine plants; all the fuci yield it in abundance ;
when burnt, their ashes are called kelp, which con-
tains a considerable proportion of this alkali. Ba~
rilla is the same, procured by burning a plant of
that name in Spain. Soda is also found in large
quantities in different parts of the earth, particu-
larly Egypt ; and common sea-salt consists of it
united to muriatic acid.
In all these cases, however, the soda is com-
bined with carbonic acid. Of this there are two
varieties, the carbonatey obtained by dissolving the
soda of commerce and crystallizing it, and the bi-
SODA. Hfi
carhonate, obtained by passing a stream of" carbonic
acid gas through a solution of the former.
Soda and potash considerably resemble each
other, but the former does not deliquesce so as to
liquefy, as potash does ; its crystals, however, efflo-
resce or fall to powder. It is used in the manufac-
ture of soap and of glass.
Soda, also, like potash, consists of a metallic
base united t oxygen. The metal is called sodium.
It resembles potassium in most of its properties.
It unites with chlorine, forming chloride of potas-
sium ; this is the common sea-salt so much used in
food, and was, till lately, called muriate of soda.
Common salt exists in immense quantities in na-
ture, both in the form of a rock, as rock-salt, which
is dug out of the earth in a solid form, and also
dissolved in the sea^ from which it is obtained by
evaporation.
Common salt is decomposed by sulphuric acid.
The sodium is converted into soda, by taking oxy-
gen from the M^ater of the sulphuric acid, and the
chlorine combines with the hydrogen of the water
thus set free, and forms hydro-chloric acid gas^
which is the same with what has been called muri-
atic acid gas. This gas, absorbed by water, forms
muriatic acid. Hence, since muriatic acid was
thus procured from sea-salt, it was supposed to
exist in it, combined with soda, whence the name
muriate of soda.
Soda unites with all the acids, forming neutral
salts, the most remarkable of which are the fol-
lowing : —
Sulphate ofsoda, called formerly Glauber's salts,
is formed abundantly in the process for procuring
the muriatic acid from common salt ; the sulphuric
acid which is employed uniting to the soda.
G 2
84 LITHIA.
Borate ofsoda^ or borax, and
P/fOsphaie of soda, useful as a test.
The fixed alkalies readily combine with oils, and
tluis form soap. Soap is soluble in water, and
owes its detergent quality to the alkali contained in
it. Alkali by itself would be too powerful, and
would be apt to destroy the linen and other sub-
stances to be cleaned.
Soap when in solution is decomposed by acids,
which unite with the alkali ; hence if an acid is
contained in water, the soap curdles. Neutral
salts formed by acids with bases of the earths pro-
duce the same effect. Hard waters are such as
have earthy salts, and are unfit for washing ; soft
water is that which is quite free from salts.
Hard soap is made from soda rendered caustic
by lime, and olive-oil, or tallow. Soft soap is com-
posed of potash and whale-oil.
LITHIA.
This alkali was lately discovered by M. Arfvred-
son, a Swedish chemist. It is found to be a con-
stituent of certain stones, and has been met with
in the petalite, spodumen, and lepidolite. Jt is of
the class of fixed alkalies ; is soluble in water, has
an acrid taste, and changes vegetable blues to
green. It forms neutral salts with the acids.
Lithia, like the other fixed alkalies, has been
found by analysis to be the oxide of a peculiar
metal, which has been called Lithium. Its decom-
position has been effected by the voltaic pile, but
the quantity of metal obtained has been extremely
small.
85
AMMONIA.
This substance is known also by the name of the
volatile alkali. It is composed of nitrogen and
hydrogen. In its purest form it is in the gaseous
state. It is then called ammoniacal gas.
Ammoniacal gas is procured by adding dry
quicklime to muriate of ammonia, and exposing
them in a retort to the heat of a lamp. The mu-
riatic acid, having a stronger attraction for the lime
than it has for the ammonia, leaves the latter, which
is disengaged, in the state of gas. A pneumatic
apparatus is necessary for this purpose, as this gas
is rapidly absorbed by water. Ammoniacal gas
has a strong pungent smell, and suffocates animals
immersed in it. It changes vegetable blues to
green. If water be introduced into the apparatus,
in contact with the gas, it absorbs it entirely, and
acquires its peculiar smell : this is a solution of
ammonia in water, and is called liquid ammonia.
Ammonia exists as a constituent in animal
bodies ; and it is obtained from bones, horns, &c.
It is a valuable material in manufactiu'es and
medicine. Ammonia forms with the acids several
valuable compounds.
With carbonic acid it forms carbonate and hi-
carbonate of ammonia. The carbonate may be
obtained by mixing ammoniacal gas with carbonic
acid gas over mercury. The two gases inunedi-
ately combine and form a solid white body, which
still retains some of the pungent smell of the am-
monia. This is the common smelBig salts. The
bi-carbonate is procured by causing a current of
carbonic acid gas to pass througli liquid ammonia.
It has no smell.
G S
86 EARTHS.
Muriate of aynmonia wxi called sal ammoniac
from its having been originally brought from the
neighbourhood of the Temple of Jupiter Ammon.
It is now abundantly prepared in this country by
saturating carbonate of ammonia with sulphuric
acid, which forms sulphate of ammonia : by de-
composing this salt by muriate of soda, muriate of
ammonia and sulphate of soda are obtained. Sal
ammoniac is employed in many processes.
EARTHS.
At the first view it would seem, from the vast
variety of soils on the surface of the globe, and
the number of rocks and stony substances, that the
different earths of which they are composed
were innumerable : nevertheless, their number is
very limited, and, by the mixture of these, the
greatest part of mineral bodies is composed.
The earths were formerly considered as ele-
mentary substances, but late discoveries have
shown that most of them are, like the alkalies, me-
tallic oxides. It is found, however, more conve-
nient still to consider them as a separate class.
The earths are of two kinds :
1. Those which have some of the properties of
alkalies and which are called alkaline earths.
2. Earths simply so called.
The alkaline earths are, lime, magnesia, barytes,
and strontia. They unite with acids forming com-
pound salts as alkalies do : like tliem they change
vegetable blues to green ; they have a considerable
degree of causticity and taste, and are soluble in
water.
LIME. 87
The rest of the earths are insipid, and are scarce-
ly at all soluble in water, and have no action on
vegetable colours.
I.IME.
Lime is one of the most abundant substances in
nature. It is the chief constituent in vast moun-
tains and rocks, and is very generally distributed,
mixed with other earths. Chalk, marble, calcare-
ous spar, and all those rocks called lim.e-stones, con-
sist of it.
In these substances, however, the lime is not
pure or uncombined. It exists in them united to
carbonic acid, constituting carbonate of lime.
To obtain pure lime, these stones are exposed
to a white heat, by which the carbonic acid is
driven off in the gaseous state. This is called the
huriiing of lime. The stone so treated is then
called quicIiHme; or, in chemical language, properly
lime.
Quicklime, or pure lime, is white ; has a hot
acrid taste, and is caustic, or corrodes the skin. It
changes vegetable blues to green.
Until the discovery of the bases of the alkalies by
Sir Humphry Davy, lime, as well as all the other
earths, was considered as an elementary substance ;
but it has been ascertained to be the oxide of a
metal to which the name of calcium has been given.
From the extreme difficulty, however, in reducing
lime to this state, the properties of calcium are but
little known. It is white and solid, resembling
silver, and soon returns to the state of oxide or
lime by attracting oxygen from the air.
When water is thrown on quicklime just burnt,
it swells, bursts, and falls to powder; giving out, at
G 4
88 LIME.
the same time, much steam and heat. This is called
the slaking of lime. In this process, the water miites
to the hme, and becomes soUd ; for slaked lime is
quite dry. It is, therefore, called a hydrate of
lime.
Lime is soluble in water : the solution has an
acrid taste, and is called lime-watei\ When lime-
water is exposed to the air, a stony film forms upon
the surface, owing to the lime attracting carbonic
acid, and returning to the state of carbonate, which
is insoluble in water. This film breaks, falls down,
and is succeeded by others in succession. Fresh
quicklime has a strong tendency to attract mois-
ture from the air, and also carbonic acid, so that it
must be kept in closely-stopped vessels.
Quicklime is used for making mortar for build-
ing, by mixing it with sand. This, by solidifying
the water and attracting carbonic acid, becomes a
very hard substance like stone. The lime should
be newly burnt, and the sand silicious and free from
impurities. It is also extremely valuable as a ma-
nure when put upon the land.
Carbonate of lime is not caustic, nor soluble in
water. It is decomposed by the stronger acids.
Put chalk or marble into a vessel, and pour upon it
diluted sulphuric or muriatic acid ; an efferves-
cence will ensue, which is owing to the escape of
the carbonic acid. Hence these acids are em-
ployed to distinguish lime-stones.
Lime combines with phosphorus, forming j)hos-
phuret of lime, to be afterwards described. With
sulphur it forms siilphuret of lime.
It also combines with all the acids, forming a
great number of neutral salts.
Sulphate of lime, called also gypsum, exists largely
in a natural state. When burnt, it forms the sub.
MAGNESIA. BAKYTES. 89
stance called plaster of Paris, so much employed
in making casts of statues, and in plastering
rooms.
Filiate of lime, or lime united to the fluoric acid,
is the substance so well known by the name of Der-
byshire spar, and which is much used for vases and
other ornaments.
Nitrate of lime is a very soluble salt ; its taste is
acrid and bitter. It is often found efflorescing on
old plaster walls.
MAGNESIA.
This earth, when pure, is white, nearly destitute of
taste and has no smell. It is insoluble in water, but
changes vegetable blues to green, and unites to the
acids. It is conjectured to be composed of a me-
tallic base, magnesiumy united to oxygen ; but the
metal has not yet been distinctly obtained.
Native magnesia is a rare substance, but it en-
ters as a constituent in many rocks, as serpentine,
steatite, &c.
Carbonate of magnesia is extensively employed
as a medicine. When a red heat is applied to it
it loses its carbonic acid, and becomes calcined
magnesia.
Sulphate of 7nagnesia is known by the name of
Epsom salt, because formerly procured from the
springs of Epsom, in Surrey.
BARYTES.
This earth was formerly called terra ponderosa,
from its great specific gravity. It has strong alka-
line properties, a caustic taste, and changes vege-
table blues to green.
90 STRONTIA. SILICA.
It slakes in the air like lime, is soluble in water,
and also in alkohol, the flame of which it causes
to assume a yellow colour. It is a deadly poison.
It is also found to consist of oxygen and a metallic
base called barium.
Carbonate qfbarytes is found as a mineral, but it
is not abundant.
Sulphate of barytes is found native more fre-
quently. When calcined, it forms the Bolognian
2)hosphorus.
Barytes is used as a white paint under the name
of permanent whiter not being liable to change its
colour.
STRONTIA.
The name of this earth is derived from Strontian,
in Argyllshire, in Scotland, where it was first dis-
covered by Dr. Hope.
It is soluble in water, and changes vegetable
blues to green.
It is also considered to be the oxide of a metal
called str^ontium.
Strontia is not very abundant, and is always in
nature found combined with the carbonic or sul-
phuric acids.
The other salts of strontia are but little known.
All the salts of Strontia have the property of tinge-
ing the flame of alkohol red.
SILICA.
This earth, which forms a large portion of the
surface of the earth, exists nearly pure in flint and
rock-crystal : hence it has been called the earth of
flints.
It may be obtained pure as follows : calcine
ALUMINA. 91
gun-flints tiil they become brittle, then pulverize
them. Mix this powder with three or four times its
weight of carbonate of potash, and fuse the mixture
in a crucible, by a strong red heat. We shall thus
obtain a compound of alkali and siliceous earth :
dissolve it in water, and add to it diluted muriatic
or sulphuric acid ; a precipitation will take place,
which, when well washed, is pure silex.
Siliceous earth, when pure, is white and tasteless.
It is infusible by itself, and insoluble in water. It
has a harsh feel, and does not form a cohesive mass
with water.
No acid can act upon it, except the hydro-
fluoric, which dissolves it. When mixed with an
equal weight of carbonate of potash, and fused in a
strong furnace, it forms glass. With a larger pro-
portion of alkali it forms a substance soluble in
water, which has been called silicated alkali. The
solution of this was called liquor ofjiints. The silex
is precipitated from it in the state of a gelatinous
hydrate by acids.
It is supposed that silica consists of oxygen
united to a certain base, which has been assumed
to be a metallic substance, and w^liich has been
called Silicium : but its real nature has not been
ascertained. It is imagined, however, that silicium
forms an alloy with iron, and that the properties of
some sorts of iron are owing to the addition of this
substance.
ALUMINA.
This earth forms a part of all clays, and hence has
been called argillaceous earth. It exists also in nu-
merous rocks, particularly slate, and even consti-
tutes some of the hardest gems and stones, as the
sapphire, ruby, and corundum.
92 CLAY. — YTTRIA.
It rarely occurs in a pure unmixed state. But it
has been found native, in small masses, at New-
haven, in Sussex, and also in Hall, in Saxony.
Clay consists of this earth, joined to silex. For-
celain clay proceeds from the decomposition of
felspar ; it consists of silica, alumina, and some-
times a little lime and potash. Pipe-day^ and
'potters' 'day are pure clays, but of variable com-
position.
Alumina has no smell nor taste 5 is insoluble in
water, but forms with it a ductile paste, and shrinks
much when exposed to heat. It is dissolved by
the liquid fixed alkalies, and unites chemically with
barytes, strontia, lime, and magnesia. It is dis-
solved by most of the acids.
The salt called alum^ which gives its name to
this earth, is a sulphate of alumina and potash.
Sulphate of alumina alone will not crystallize ; but
when sulphate of potash is added, octahedral crystals
of alum are produced. When alum is exposed to
heat, it loses part of the acid and water of crystal-
lization, becomes light and spongy, and is called
humt alum. Alum is extensively employed in the
arts of dyeing and calico printing, in consequence
of the attraction which alumina has for colouring
matter. Alumina also forms the basis upon which
are precipitated certain colours used as pigments.
YTTRIA.
This rare earth, so called from Ytterby, in Swe-
den, where it was discovered, is found only in a
stone called gadolinite, so named from Professor
Gadolin. It is insipid, and insoluble in water, but
dissolves in carbonate of ammonia. It forms salts
Vd
GLUCINA. — ■ZIRCONIA.— ^THORINA. 9^
which have a sweetish taste. Its specific gravity is
greater than that of any other earth. The base of
yttria has been supposed to be a metaUic substance,
which would receive the name of yttrium ; but it
lias never been exhibited in a separate state. Yttria
contains oxygen, and hence been inferred to be a
metallic oxide.
GLUCINA.
Ghicina, or Glucinej is an earth which has been
procured only from the beryl, the emerald, and the
euclase.
It derives its name from its forming salts which
have a sweetish taste. It has no taste nor smell, is
infusible by heat, but dissolves in the acids, and
pure alkalies. It is insoluble in water. It is also
supposed to be a metallic oxide.
ZIRCONIA.
Zirconia is a very rare earth, found as yet only
in the zircon or jargon of Ceylon, and the hyacinth.
It is void of taste or smell ; is insoluble in water
and pure alkalies ; but is soluble in alkaline car-
bonates. Its base is supposed to be metallic.
THORINA.
This is another very rare earth, discovered by
Berzelius, who extracted it from a species of gado-
linite. It absorbs carbonic acid, and dissolves
readily in acids. It is not soluble by the pure
alkalies, but slightly so by the alkaline carbonates.
It is supposed to be the oxide of a metal.
94,
METALS.
We come now to treat of the last division of the
metaUic substances ; those which, remaining in the
air in the metaUic state, have received the name
particularly of metals.
Those metals whose combinations with oxygen
form alkalies, as potassium, sodium, and lithium, as
also those whose oxides form earths, as calcium,
magnesium, barium, strontium, silicium, alumium,
yttrium, glucinum, zirconium, and thorinum, have
been already mentioned incidentally, in speaking of
the alkalies and earths to which they give rise. But
we shall now enumerate the general properties of
this important class of bodies, including the above
mentioned.
The metals are distinguished from all other sub-
stances by certain properties, particularly a pecu-
liar lustre ; and most of them have great weight, or
specific gravity.
Several of them have been known to part of the
world in ^ery ancient times, while some savages in
the present day are totally unacquainted with their
use : but a considerable number of the metallic sub-
stances have been discovered only lately. The
metals are so important in many mechanic arts,
that mankind could never have attained their pre-
sent state of civilisation without them.
Metals are, in general, solid bodies at the usual
temperature : one only, mercury, is fluid.
They are opaque in the mass in its usual state ;
but gold, when beat into very thin leaves, transmits
a faint greenish light, when held between the eye
and the direct rays of the sun.
METALS. Q5
Tlie lustre by which they are distinguished,
called the metallic lustre, is not easily described, but
may be exemplified in that of silver, steel, lead, tin,
SiC, as distinguished from that of glass, diamond,
&c. Mica has a lustre which approaches that
called the metallic, but it loses this on being
scratched, while the metals do not ; on the con-
trary, they are more brilliant when fresh cut. This
property of the metals renders them highly useful
for ornamental purposes, and for reflecting light,
as in mirrors.
Metals are the best conductors of heat, and also
of electricity.
Some of the metals are capable of being extended
under the blows of a hammer, which property
is called malleahilityj and is peculiar to metals.
Others, again, are brittle, on which account they
were formerly called sejui-metals. The malleable
metals are, gold, platina, silver, palladium, potas-
sium, sodium, mercury in its frozen state, copper,
iron, lead, tin, zinc, and nickel. These differ
much in their degrees of malleability. Gold may
be beat into the thinnest leaves, and zinc is very
little malleable, except when heated. The malle-
able metals are also ductile, or may be drawn out
into wire. Gold and platina may be drawn into
the finest wire.
One of the metals, iron, is capable of being
made very elastic, which renders it fit for making
springs.
Most of the metals are very fusible, or capable of
being rendered fluid by the application of heat;
on this account they may be cast into moulds, and
formed into various utensils: some of the metals
are volatile at a high degree of heat.
None of them are very hard naturally ; but some
96 METALS.
of them may be hardened by art: thus the moderns
make cutting instruments of iron and steel, and
the ancients made them of a combination of cop-
per and tin.
All the metals are capable of combining with
oxygen, and thus forming oxides ; but they differ
very much in the readiness with which they com-
bine with it, which occasions their division into
several classes.
The oxides of metals have none of the metallic
brilliancy, and no malleability : their appearance
and nature are totally different from that of the
metals themselves.
The oxides of some metals, as potassium and so-
dium, are alcaline ; others are acid, constituting the
metallic acids : the rest have neither acid nor alca-
line properties, but are, as well as others, capable
of being dissolved by the acids, thus forming salts.
Some of the metals attract oxygen so strongly,
tliat they become oxidized almost immediately in
the open air, and even take oxygen from all its
combinations, so that they are, with great difficulty,
preserved in the metallic state ; of this nature are
metals that produce the alkalies and earths, which
can only be kept in pure bitumen called naphtha,
which has no oxygen in its composition.
Some of the metals do not experience any
change on being kept in fusion by a strong heat
with an access of air ; but others are by this means
converted into oxides. The first have been called
perfect metals, and comprehend gold, platina, sil-
ver, and palladium. The rest differ very much in
the degree of heat necessary to oxidize them.
Arsenic, manganese, and the bases of the earths
and alkalies become oxides at the usual temperature
of the atmosphere, even when perfectly dry. Lead
METALS. 97
and copper are oxidized slowly by moist air. Iron,
zinc, copper, tin, &e., require to be heated to red-
ness. Although the perfect metals cannot be
oxidized by any degree of ordinary heat, they may
by the effect of electricity and galvanism. All the
metals, that are converted into oxides by atmo-
spheric air, undergo this change still more rapidly
in oxygen gas, as was shown in the burning of iron
wire in oxygen.
Metals are also converted into oxides by the ac-
tion of acids, but in different manners. Some acids
which contain oxygen loosely combined part with
it to the metal ; while others, as the sulphuric and
muriatic acids, do not act upon iron or zinc, except
they are diluted with water, and then it is the wa-
ter, and not the acid, which supplies the oxygen.
Metals cannot be made to combine with all pro-
portions of oxygen, but are susceptible only of cer-
tain degrees or stages of oxidation. Thus iron has
only two oxides j the black oa:ide composed of 29.5
parts of oxygen, and 100 parts metal ; and the
red oxide of 43.5 parts of oxygen, and 100 parts of
metal : and there are no intermediate degrees of
oxidation, nor will iron combine with a larger or
smaller proportion of oxygen. Metals differ in the
number of oxides which they form : thus some
have two, some three, and others four oxides :
and, according to the law of the atomic theory,
the different oxides of the same metal contain oxy-
gen in proportions that are simple multiples of each
other.
The different oxides of the same metals have dif-
ferent colours, which render them very valuable as
pigments. They have also distinct chemical pro-
perties, and combine, in different proportions, with
the acids, forming distinct salts.
VOL. II. II
98 PLATINA.
All the metals are considered as simple bodies,
none having been decomposed or resolved into
other principles ; also, at one time, they were sup-
posed to be formed of a peculiar basis and an ima-
ginary inflammable principle called plilogisto7i.
This theory was very favourable to the idea of
forming metals, and transmuting or changing them
into each other. The existence of phlogiston is no
longer believed in, and the science of alchemy is
only remembered as affording an instance of the
dangers of false theories, and of the great credulity
of persons in many respects well informed.
The oxide of a metal was formerly called a cal^r^
and its conversion was supposed to be owing to the
loss of the phlogiston ; but it was observed that
the metal gained instead of losing weight by this
change ; in fact, it acquires just the weight of the
oxygen it combines with. When the oxides of me-
tals are made to part with their oxygen, hey are
reduced to the metallic state, and upon this
depends the art of reducing metals from their
ores.
PLATINA.
This metal was unknown in Europe before 1748,
and is still chiefly found in South America : it has
been also found in Estremedura, in Old Spain.
In colour it is nearly as white as silver. It is
very difficult of fusion, and can only be melted by
the assistance of oxygen gas or by galvanic elec-
tricity. From its refractory quality, it is employed
for crucibles and other chemical utensils exposed
to heat, for which it is admirably adapted.
It is also extremely ductile and malleable, and
may be drawn into very thin wire, and hammered
into thin plates.
GOLD. 99
Platina does not tarnish on exposure to the at-
mosphere, and takes an excellent polish, on which
account it is used in making specula for telescopes.
It is also capable of being welded, a property only
possessed by it and iron. It is the heaviest of the
metals ; its specific gravity being nearly 22.
Platina is readily dissolved by the nitro-muri-
atic acid and by chlorine, but is not acted upon
by any other acid. It also combines with sulphur
and phosphorus.
Platina is brought to Europe in small flattened
grains, which, however, are not pure platina, but
contain a mixture also of nine other metals. Four
metals, osmium^ iridhmiy rhodhwiy and palladium,
were unknown till they were discovered in these
gi'ains.
GOLD.
Gold is found in nature in a metallic state. It
is generally met with in grains called gold-dust,
mixed with the sands of rivers, either b^ng carried
away by them from the rocks which contain it, or
having been deposited in ancient alluvium. It is
chiefly found in Africa, also in Brazil and Peru.
There are mines of it also in Hungary ; and it is
met with in quantities too small to be worth work-
ing, in the sands of many rivers of Europe.
Lately some was found in the county of Wick-
low, in Ireland ; one grain weighed 22 ounces, and
considerable expectations were formed ; but, not-
withstanding, the works were abandoned as unpro-
ductive.
Gold is the heaviest of the metals except platina.
It is of a rich yellow colour, and not ^ ery hard
when pure.
II 2
100 ' GOLD.
It melts at a bright red heat, but cannot be oxi-
dated by any furnace, though it may by electricity
and galvanism. It does not oxidate in the air ;
hence it is so useful in gilding, its beautiful lustre
remaining untarnished.
It is the most ductile and malleable of the me-
tals, and may be drawn into the finest wire for gold-
lace and other purposes, and may also be hammered
into leaves of extreme thinness for gilding.
Gold is not acted on by any acid except the
nitro-muriatic acid and chlorine. From this pro-
perty the former was named aqua-regia^ gold being
called by the alchemists the king of the metals.
The solution of gold, called muriate of gold, yields
by evaporation crystals of a beautiful yellow co-
lour, which, when dissolved in water and precipi-
tated by a solution of tin, afford the beautiful pow-
der called the purple precipitate qfcassiuSy much
used in enamelling. This consists of oxide of gold
mixed with oxide of tin.
If any substance, as a piece of ribband, be dipped
into the muriate of gold, and then exposed to a
stream of hydrogen gas, the gold will be revived,
and the substance covered with it. Some com-
bustible bodies attract the oxygen from the solu-
tion of gold, and cause it re-appear in its metallic
state. Thus, if a piece of charcoal be put into a
glass-jar containing a diluted solution of gold, and
exposed to the direct rays of the sun, it will soon
appear gilt. When ammonia is added to a solution
of gold, a yellow precipitate is formed, called ^ful-
minating gold, because it has the property of ex-
ploding when exposed to heat.
If to a solution of muriate of gold, sulphuric ether
be added, the gold will combine with the ether,
15
leaving the acid, and wilt float on the surface of the
fluid. If pohshed steel be dipped into this, it will
be covered with a coating of metallic gold. This
process is employed for gilding lancets, and other
surgical instruments, to defend them from rust.
Gold easily alloys with mercury, which is, there-
fore, much employed for extracting it from the
substances with which it is mixed in its natural
state. The mercury, being volatile, is driven off
by heat, and the gold remains free.
Gold in its purest state is too soft to be used as
coin ; it is, therefore, alloyed with n of copper.
Jeweller's gold generally contains considerably
more.
Gold seems to have been one of the earliest
known of the metals. The ancients were lavish
in its use, and it is still frequently used in orna-
ments among savage tribes.
SILVER.
Silver is often found native, or in the metallic
state, but it is most usually combined with other
metals, or sulphur. In its native state it fre-
quently assumes an arborescent form. The richest
silver mines are in Mexico and Peru ; but others
exist in many countries. Lead ore very frequently
contains a quantity of silver, and sometimes it is
worth extracting.
Silver is of a brilliant white colour. It is very
ductile and malleable ; may be drawn into fine
wire, and beaten into thin leaves ; but it is inferior
to gold in these qualities.
Silver fuses when heated red hot, and may be cast
into moulds, but is not thus converted into oxide
H 3
lOi . SILVER.
by any continuance of heat: it is oxidized by
common and galvanic electricity.
It is not oxidized by the air ; but it is tarnished
by exposure, because the sulphurous vapours form
with the metal a sulphuret of silver.
Oxide of silver is of a dark olive colour, and is
obtained by precipitating it from the nitrate of
silver by lime-water, this metal being soluble in
the nitric acid.
Nitric acid can dissolve more than half its weight
of silver, the solution depositing crystals. When
these are fused by a gentle heat, they may be
poured into moulds, and form the substance called
luna7' caustic^ used in surgery.
Nitrate of silver is used by chemists as a test for
muriatic acid; for if it be dropped into any
liquid containing muriatic acid, a white precipi-
tate will appear, owing to the superior affinity of
silver to muriatic acid, and to the insolubility of
muriate of silver. Nitrate of silver is very caustic,
staining animal and vegetable substances of a
black colour, and hence it is employed as a ]ier-
7na7ient marking ink for linen, and also for staining
hair ; though for this last purpose it should be used
with great caution, and much diluted.
If a few drops of the nitrate of silver be put
upon a piece of glass, and a copper wire be placed
in it, a beautiful metallic precipitation of the silver
will appear in an arborescent form.
When silver is precipitated from its solution in
nitric acid by ammonia, it forms fulminating silver,
M'hich is a dangerous preparation ; for it explodes
by the slight contact of a body.
When mercury is added to the nitric solution of
silver, a precipitation of metallic silver is Ibrmed
MERCURY. 103
resembling in appearance a vegetation, and called
arbo7' Diance.
Silver is not soluble in the hydro-chloric acid
(muriatic acid), yet, when this acid is added to a
solution of nitrate of silver, it unites to the oxide,
and a white curdy precipitate falls down, which
is the muriate of silver^ or, in conformity with the
new nomenclature, tlie chloride of silver. If this
precipitate be fused by a gentle heat, a semi-trans-
parent mass is formed, called formerly lima cornea^
or horn silvery the fused muriate of silver*
Silver is also dissolved by the sulphuric acid, and
the sulphate of silver is used as a chemical test.
Silver also unites to sulphur and phosphorus.
Silver, when employed for coin is alloyed with
copper to increase its hardness. Our coin con-
tains thirty-seven parts silver and three parts
copper.
MERCURY.
This metal, called also quicksilver^ is always fluid
when in the usual temperature of the atmosphere ;
but when exposed to an intense degree of cold, it
is frozen into a solid mass, and is then malleable.
The temperature necessary for this purpose is 39*^.
The cold is sometimes so great within the polar
circle as to freeze the mercury in the thermometer ;
but in this country that can only be effected by
exposing it to a freezing mixture.
Mercury also boils at 655°, and then evaporates,
and may be distilled from one vessel to another.
It is sometimes found in nature in a pure state,
but usually it is united to sulphur, with which it
H 4
104 IRON.
forms the ore called finnabar. The greatest quan-
tity of it is found in Spain and South America.
When acted on by heat and air for a long time,
it absorbs oxygen, and is converted into a red
oxide called formerly precipitate per se : and when
the heat is increased, the oxygen is given out, and
the mercury re-assumes its metallic appearance.
When it is agitated long in air, it is converted into
the black occidcy which contains a smaller propor-
tion of oxygen than the red oxide. It is the black'
oxide which is employed in mercurial ointment.
Mercury is acted on by the acids, forming salts of
mercury. It also unites to chlorine (oxymuriatic
acid,) in two proportions, forming calomel and cor-
rosive sublimate.
Mercury when triturated with sulphur, com-
bines readily into a black compound called ethiops
mineral ; when united to a larger proportion of
sulphur, it forms the beautiful pigment called
cinnabar.
Mercury combines with several of the metals,
forming soft alloys called amalgams. The amal-
gam with tin is used for mirrors : that with zinc is
employed in electrical machines.
IRON.
ISIo metal is so universally diffused throughout
nature as iron. It is never found in the earth in
the metallic state, but is always procured from
ores.
Iron is of a bluish-grey colour. It is very duc-
tile, for it may be drawn into wire as fine as
human hair. It is also very malleable, and pos-
IRON. 105
sesses the property of being welded; that is, of
having two separate pieces united together by
hammering when red hot. It is one of the most
infusible of the metals, but may by intense heat be
melted and run into moulds. It is in its pure state
among the hardest of the metals, but may be made
to exceed all the rest in hardness when converted
into steel.
It possesses the magnetic property, the load'
stone itself being an ore of iron.
Exposed to the action of the air and moisture,
iron soon rusts or OTidates. It then attracts the
oxygen and carbonic acid, and is changed into a
reddish brown substance, which is a mixture of
oxide of iron and carbonate of iron.
Iron unites to oxygen in two proportions. The
protoxide of iron consists of one hundred parts of
iron, and twenty-nine parts oxygen ; it is of a
black colour ; hence it is called the black oxide of
irony formerly martial ethiops. It is formed when
iron is heated red hot ; scales form on the outside,
which fly off when hammered. It is magnetic.
The peroxide is red, and consists of one hundred
parts iron, and forty-three oxygen ; it is called the
red oxide of iron. The red oxide is formed by
keeping iron filings red hot in an open vessel, and
agitating them constantly till they are converted
into a dark red powder, formerly called saffron of
Mars.
Iron is acted on by all the acids, and various
salts of iron are formed : the most remarkable are
the following : —
Sulphate of irony formerly called copperas or
green vitriol.
Nitrate of iroUy and acetite of irdiiy used in
dying.
106 IRON.
FerrO'prussiale qfirorij called prussian blue, used
as a pigment.
Iron also combines with sulphur, phosphorus,
carbon, chlorine, and iodine.
Sulphuret of iron, composed of sulphur and iron,
is called also pyrites. Iron with carbon forms plum-
hago, commonly called blach-lead, used for making
pencils. Steel is another compound of iron with
carbon.
The ores of iron consist either of the black ox-
ide, which is called the magnetic iron oi^e, the red
oxide or the i^ed iro7i ot^e, carbonate of iron, and
clay ironstone.
The iron is separated from these ores by smelting
in furnaces, where it is made to flow out into va-
rious moulds made in a kind of loam. The first pro-
duct is called cast iro7i. It contains some carbon
and oxygen ; and, it is thought, also silicium, besides
casual impurities. Of this, cannon, pipes, grates,
and other articles of cast iron are made. It is of
two kinds : "white cast-iron is very brittle ; grey cast
iron is less brittle, though not malleable, but may
be bored and turned in the lathe.
To render iron malleable it must be freed from
those substances with which it is combined in the
crude state. To effect this, it is kept in fusion in
a furnace exposed to air and flame, and well stired.
The oxygen combines with the carbon, and escapes
in the form of carbonic acid gas ; and the earthy
matter is vitrified, and rises to the surface as slag.
It is then subjected to the action of large hammers
and rollers, by which the remainder of the impuri-
ties is forced out. It then constitutes bar iron,
also called 'wrought iron, fit for manufacturing.
AVr.ought iron is of a fibrous structure, and is the
metal in a pure slate. It is now extremely malle-
IRON. 107
able, soft, and easily filed, and also capable of
being forged and welded. There are several va-
rieties of iron in this state, arising from the ores
from which they were procured, the process of
smelting, or the intermixture of foreign substances.
One variety is called hot sJiort iron ; it is ex-
tremely ductile when cold, and on this account is
employed for making wire ; but when heated it is
extremely brittle : it is also fusible. Cold short
iron, on the contrary, is highly ductile when hot, but
brittle when cold. The causes of these qualities
are not precisely known, but it is said that the first
is iron combined with arsenic, and that the latter
contains phosphoric acid.
Iron is capable of being reduced to a third state,
which is that of steel. It is converted into steel,
by exposing it to heat in contact with carbonaceous
substances, which unite themselves with it. Steel
is, therefore, iron united to carbon, and is made by
three processes.
Natural steel is made by keeping cast iron in a
state of fusion in a furnace, its surface being all
the while covered deep with scoriee ; part of the
carbonic acid gas escapes, while another part com-
bines with the iron. This steel is inferior to the
other kinds.
Steel of cementatmi is made by placing bars of
iron in charcoal powder, and exposing them to a
strong heat in a furnace for six or eight days.
The iron and the carbon thus combined constitute
what is here called blistered steel. When this is
rendered more malleable by the operation of the
hammer, it is called sheer steel.
Cast steel is made by fusing bhstered steel with
pounded glass and charcoal powder, in a close cru-
cible. It is also made merely by fusing iron with
108 IRON.
carbonate of lime. This is the most useful of all the
kinds of steel, and employed for razors, surgeons*"
instruments, and similar purposes ; its grain is the
most compact, and it takes the highest polish.
It is the particular property of steel to become
extremely hard, if it be heated red hot, and then
suddenly plunged into cold water ; but different
instruments made of steel require to be of different
degrees of hardness ; and they are, therefore, sub-
jected to a process called tempering ^ which is heat-
ing them again to a certain point after having been
hardened. The tempering of steel, for some pur-
poses, is a delicate process.
A polished bit of steel, when heated with access
of air, acquires very beautiful colours. It first be-
comes of a pale yellow, then of a deeper yellow,
next reddish, then deep blue, and at last bright
blue. At this period it becomes red hot, and the
colours disappear: at the same time the metallic
scales, or the black imperfect oxide of iron which is
formed, incrusts its surface. All these different
shades of colour indicate the different tempers the
steel has acquired by the increase of heat. Artists
have availed themselves of this property, to give
to surgical and other instruments those degrees of
temper which their various uses require. Iron
may be alloyed with most of the metals, but these
alloys are not much used.
Wootz is the name given to a kind of steel made
in the East Indies, which is of a very superior
quality for cutting-instruments.
109
COPPER.
Copper is sometimes found native, but in very
small quantities. It is generally met with in the
state of oxide, or united to sulphur, or to acids.
In Cornwall there are very rich mines of copper.
Pure copper is of a red colour, very tenacious,
ductile, and malleable. It melts at 27 of Wedge-
wood's pyrometer, and burns with a green flame.
It is not oxided by water. When exposed to a
red heat, it becomes covered with a crust of oxide
of a blackish colour, this is the peroa:ide of copper.
The fir»t, or protoxide^ is of a red colour when
found native,but when formed artificially is orange.
The oxides of copper are reduced to the metal-
lic state by heating with charcoal or oils.
The nitric acid disolves copper with efferves-
cence, and the solution has a blue colour. The
acid first oxidates the metal, a large quantity of
nitric oxide (nitrous gas), is disengaged, and the
oxide dissolves ; this forms the nitrate of copper.
The sulphuric acid does not dissolve copper un-
less when concentrated, and in a boiling state.
Fine blue crystals, which are the sulphate of copper,
are the result. This is what is commonly called
blue vitriol. This salt is decomposed by iron ; for
if a piece of iron be immersed in a solution of sul-
phate of copper, the copper will be precipitated
upon the iron. This process is often employed for
procuring the copper from the water ir copper
mines, which has in it a large portion of sulphate
of copper.
The muriatic acid does not act upon copper ex-
cept in a state of ebullition, and then the muriate
110 COPPER.
of copper is formed, which is of a green colour, and
of an astringent taste. A solution of it is used as
a sympathetic ink ; for letters written with it will
become yellow by warming, and will disappear
again when cool.
The acetous acid in a sufficient degree of con-
centration dissolves copper, but when not concen-
trated, as in vinegar, it acts upon it very slowly, and
forms common verdigris, which is an impure
acetate of copper. This being dissolved in distilled
vinegar, and subjected to evaporation, crystals are
produced which constitute what is called distilled
verdigris.
Copper is employed in making kitchen utensils ;
but as these vessels are liable to be corroded by
the acids and fatty substances used in culinary
preparations, they often become dangerous, as all
the salts of copper are poisonous. Culinary utensils
of copper should always be well tinned, but those
of iron tinned are safer, as iron has no poisonous
quality. The alloys of copper with other metals
are very useful.
Tombac is formed of copper, arsenic, and tin.
Prince's metal, or Pinchbeck, is made of copper
and zinc.
Brass is also formed of another proportion of
copper and zinc.
Bronze is made of copper and tin.
Bell-metal is also of copper and tin, but with
more tin than the latter alloy.
A solder for silver is made of copper and
silver.
Ill
TIN.
Tin is a metal of a colour approaching to that of
silver, but somewhat duller. It is extremely malle-
able. When hammered into leaves it constitutes
tin-foil. It is not, however, very ductile. It is
nearly as soft as lead, and may be easily bent, and
then emits a crackling noise, which is peculiar to it.
Tin fuses more easily than any other metal :
when it has been kept some time in a state of
fiision, with access of air, its surface becomes
wrinkled and covered with a grey pellicle, which is
the Jirstj or grey oxide of tin. This oxide when
mixed with melted glass forms white enamel.
The grey oxide, when exposed to a greater
degree of heat, takes fire, acquires more oxygen, and
becomes of a pure white ; the white oaide of tin.
Tin is not oxidized in the air at the common
temperature ; on account of which property, it is
used for covering iron plates, to prevent tlieir
rusting.
Tin dissolves in the muriatic acid, forming muri-
ate of tin, much used by dyers.
With nitric acid it forms nitrate of tin.
Tin united with sulphur forms the aurum mus-
turn. Alloyed with lead, it forms plumber's solder.
The best pewter is composed of tin alloyed with
antimony, copper, and bismuth.
Tin is not found native, and its ores are not much
distributed. The richest mines are in Cornwall.
LEAD.
This metal is never found in a native state. The
ore from which it is chiefly procured is galena^
which is lead united to sulphur, or a sulplntrel
of lead.
112 ' LEAD.
Pure lead is of a greyish colour. When fresh cut
it is bright, but it soon tarnishes in the air. It
stains the fingers or paper when rubbed on them.
It is easily cut with the knife; has little or no elas-
ticity, and is very malleable, but not very ductile.
Water does not act upon lead. It easily fuses ; and
exposed to the air in a state of fusion, its surface
becomes covered with a grey pellicle: if this be
removed another succeeds, and in this manner the
whole may be converted into a powdery substance.
This pellicle is composed of oxide of lead mixed with
a portion of metallic lead. If it be subjected to a
strong heat, it is changed into a yellow powder,
known by the name of massicot ; which is the Jirst,
or yellow oxide of lead : it is used as a pigment.
If massicot be exposed to the flame of a furnace
for some time, and kept stirred, it is converted into
a beautiful pigment, called minium^ or red lead.
This has been called the red oxide of lead ; but it
is a mixture of the yellow oxide above mentioned,
and another, the brown oxide of lead. This brown
oxide may be procured by pouring nitric acid on
red lead j when the yellow oxide in the red lead
will be dissolved by the acid, and the brown oxide
will remain, being insoluble.
If the oxides of lead be acted on by a strong-
heat, they give up their oxygen, and metallic lead
remains ; but they are more readily reduced by
mixing them with combustible matter.
Lead, when procured from its ore, frequently
contains so much silver, that the latter is wortli
extracting. This process is called refining. Tlie
lead is played upon by the flame of a furnace, by
which the lead is oxidized, and the oxide is partly
vitrified, and assumes a scaly form, called litharge.
The silver then remains free.
LEAD. 113
The oxides of lead are easily changed into glass,
and unite with all the metals except gold and silver;
on this account they are employed for separating
other metals from these. This process is called
cupellation. The mixed metal is put into a dish
called a cupel^ made of bone-ashes, and placed in a
cupelling furnace ; the lead is oxidized and vitri-
fied, and sinks into the bone-ash cupel, carrying
with it all the baser metals.
White lead, so much used in painting, is a com-
pound of the yellow oxide and carbonic acid ; or a
carbonate of lead. It is made by exposing plates of
pure lead to the warm vapour of vinegar. By this
they are gradually corroded, and converted into a
heavy white powder, which is white lead.
When the carbonate of lead is dissolved in dis-
tilled vinegar, a salt is obtained, which crystallizes,
and is called commonly sugar of lead; more pro-
perly acetate of lead. All the salts of lead have a
sweetish taste, and are of a poisonous quality.
The affinity of the muriatic acid (hydrochloric
acid) for the oxides of lead is so great, that the
latter decomposes all the combinations of this acid.
They decompose the muriate of soda (common salt),
and thus form muriate of lead, which, on fusion,
affords minei^al oy patent yelloxv.
Sulphuric acid does not act on lead when cold;
but dissolves it at a boiling heat, and forms sul-
phate of lead, which is insoluble in water.
Chr ornate of lead , or chromic acid and lead, is a
very beautiful yellow pigment. It is found native
in small quantities, but is now prepared largely by
art. Lead is one of the most useful metals. It
is much employed in covering houses, when made
into thin sheets by casting or by milling. It is used
also for water-pipes and cisterns, and for a variety
VOL. II. I
Il4 ZINC.
of well-known purposes. Its oxides are used in
the manufactures of glass, and the glazings of
earthenware; also as pigments. Preparations
of lead are also used as external applications in
diseases. The alloys of lead with tin form solder,
and other alloys are employed in various arts.
ZINC.
This metal is chiefly procured from calamine^
which is a liydy^ated oxide of zinc ; and from blende,
a sulphuret of zinc.
Zinc is a whitish metal of the colour of tin. It
is slightly malleable when cold ; but heated to
between 200° and 300° it is very malleable, and
has been manufactured into nails, drawn into wire,
and made into sheets.
It is often known among workmen by the name
of Spelter, It is easily fused, and is the most in-
flammable of the metals; thin leaves of it will take
fire with the flame of a taper.
It is scarcely oxidized in the air at common
temperatures, but is rapidly converted into oxide
when kept melted in an open vessel. Its surface
then becomes covered with a grey pellicle, which
is oxide of zinc. When zinc is made red hot in an
open vessel, it takes fire and burns with a brilliant
flame, sending off white flakes of oxide. These
have been calledj^ower^ of zinc.
Zinc decomposes water very slowly when cold ;
but with great rapidity when the vapour of water
is brought into contact with it ignited.
Zinc dissolves very readily in diluted sulphuric
acid; forming thus sulphate of zinc, or "white vitrioL
During this solution, a great quantity of hydrogen
ANTIMONY. 115
gas is disengaged, and this is one of the best modes
of procuring that gas.
The nitric and muriatic acids also act upon zinc.
Zinc combines with phosphorus and sulphur.
It can be alloyed with most of the other metals.
With copper, it forms brass,
ANTIMONY.
Antimony is rarely found native. It is procured
from an ore called crude antimony, which is a sul-
phuret of antimony.
Antimony is of a silvery white colour. It is so
brittle, that it may be pulverised in a mortar ; and
its interior texture appears to be scaly or lamellar.
It requires 800° to fuse it. It does not change in
the air, but when kept in fusion at a red heat, it
emits white fumes, consisting of an oxide formerly
called^oa;er5 of antimony.
There are two oxides of antimony. The protox-
ide is procured by precipitating the muriate of
antimony by potash. It is of a grey colour. The
peroxide is formed by causing the nitric acid to act
upon the metal, or by collecting the fumes already
mentioned as the flowers of antimony. It is white.
The oxidesof antimony are very valuable medicines.
Tartrate of potash and antimony form emetic tartar,
Jameses powder is composed of phosphate of lime
and antimony. Kermes*s mineral is made from sul-
phuret of antimony by potash.
Antimony is also used in printers' types ; and in
specula for telescopes. The sulphuret has been
used for staining hair black.
116 BISMUTH. — ARSENIC.
BISMUTH.
Bismuth is found native, and also combined with
sulphur and arsenic.
It is of a reddish white colour, brittle, and easily
fusible. It is not quite so hard as copper. It
is not oxidated by water; it tarnishes in the air,
but does not undergo any other change. Kept
melted in an open vessel, its surface becomes
covered with a dark grey pellicle, which is renewed
till the whole is converted into oxide.
The oxide of bismuth is a yellow powder. When
strongly heated it melts and becomes darker
coloured.
Bismuth dissolved in the nitric acid, affords a
white powder, if water be added to the solution.
This is the magistry of bismuth^ ov pearl 'white, which
has been used as a cosmetic, but very improperly,
as it is apt to turn black by sulphuretted hydrogen.
Bismuth dissolved by the acetic acid forms a
sympathetic ink. The characters written with it
are invisible, until they are exposed to sulphuretted
hydrogen, when they appear black.
Bismuth alloys with all the metals, and has the
property of giving them great fusibility. If eight
parts of bismuth, five of lead, and three of tin be
fused together, they form what is called the fusible
metal, which melts in boiling water. On this ac-
count bismuth enters into the composition of some
of the soft solders.
It has also the property of rendering gold ex-
tremely brittle.
ARSENIC.
Arsenic, the poisonous effects of which are so
well known, is a metallic substance, sometimes
NICKEL. 117
found native, but oftener combined with sulphur.
The sulphuret of arsenic is called orpiment.
Arsenic is frequently mixed in metallic ores,
and is driven off by heat. It is known by its pecu-
liar smell, like garlic.
The colour of metallic arsenic is grey; it is very
brittle. It soon loses its metallic lustre in the air,
and becomes black. The oxides of arsenic have
acid properties. There are two: the white oxide
of arsenic is called arsenious acid. It is highly
poisonous. It is soluble in water. It reddens
vegetable blues. It is of a white colour, is semi-
transparent, and brittle. Its taste is acrid, with a
nauseous sweetness. The best way of getting rid
of its action as a poison, when taken into the sto-
mach, is to produce vomiting and purging.
Arsenic acid is a white deliquescent substance, of
a sour taste, obtained by distilling nitric acid off
metallic arsenic. It forms salts with several of the
metals. Arseniate of iron crystallizes in cubes of
a green colour. The arseniates of copper are
among the most beautiful minerals. The alloys of
arsenic with some of the metals are used for some
purposes. It is mixed with lead to assist its
granulation in making small shot. It is also used
in making flint glass, and in calico-printing.
NICKEL.
Nickel is a rare metal. It is white, much resem-
bling silver*, and possesses, like iron, the magnetic
property. It is not easily fused, and it is malleable.
It is rather softer than iron, and soon tarnishes in the
air. It is found native, and combined with arsenic.
Nickel dissolves in the acids, and its salts are
distinguished by their fine green colour.
I 3
us ivAnganese.
It forms two oxides, the black and the grey.
Nickel alloys with most of the metals, and it is
found alloyed with iron in those masses that fall
from the atmosphere, called meteoric stones. The
origin of those lapideous masses that appear in so
extraordinary a manner is entirely unknown: but
the numerous well-authenticated accounts we have
had of the fact put it now beyond dispute. They
are first seen as large meteors, at a great height in
the air, which suddenly burst with an explosion,
and the fragments are seen to fall to the earth. It
is very remarkable that their composition is always
the same, although they have fallen at many difter-
ent times, ,and in different places. They always
contain native iron alloyed with nickel, in grains
imbedded in a stony matter. The substance of
these meteoric stones is not like any bodies which
are found in the earth. In 1795, one weighing
56 lbs. fell in Yorkshire.
MANGANESE.
This metal is never found native. Indeed its
attraction for oxygen is so powerful, that it is with
difficulty preserved in the metalHc state. When
pure, it is of a greyish colour, much like cast iron,
and not malleable. It soon tarnishes, and at last
becomes black. This change takes place more
rapidly, if the metal be heated, or put into water.
There appear to be two oxides of this metal ; the
protoxide^ which is of a greenish colour ; and the
peroxide, which is steel black, and has a consi-
derable lustre: the latter is found in abundance,
particularly near Exeter, and is much used in
bleaching, and also for procuring oxygen gas, as
it parts with it simply by the application of heat. It
COBALT. 119
contains one-third of its weight of oxygen. This
oxide is sometimes very beautifully crystallized.
Manganese is also employed by glass-makers to
destroy the greenish tint of glass, and for making
violet-coloured glass.
Almost all the salts of manganese are soluble in
water.
COBALT.
Cobalt is never found but in a state of combin-
ation. It is met with united to sulphur, arsenic, and
other metallic substances.
The ores of cobalt had been long used for giving
a blue colour to glass, before its metallic nature
was known.
The metal itself is not applied to any use. When
pure, it is a reddish grey colour ; rather soft and
brittle. Like iron, it is attracted by the magnet.
It is not oxidized by the air nor by water. It is
converted into a deep blue by exposure to heat
and flame.
There are two oxides of cobalt. The 'protoxide
may be formed by precipitating by potass, a solu-
tion of cobalt in nitric acid. It is of a blue colour
when first precipitated, but becomes black by
absorbing oxygen. To recover the blue colour, it
must be heated red hot, by which the oxygen is
expelled. This oxide dissolves in acids. The mu-
riate of cobalt is green, and forms a sympathetic
ink. Letters written with it are invisible, until they
are warmed, and then they appear of a fine green j
when cold they disappear again.
The peroxide of cobalt is procured by drying in
the air, with heat, the protoxide just precipitated;
by this the protoxide absorbs oxygen, and becomes
the peroxide. It is black.
I 4
120 MOLYBDENA. — TUNGSTEN.
Ores of cobalt are very valuable. Zaffre is a
substance produced by roasting the ores of cobalt,
by which the volatile matters (generally arsenic
and sulphur,) are driven off; the remainder is then
fused with sand or pounded flints. A blue glass is
thus formed, which, when ground and washed, con-
stitutes the pigment called smalt.
MOLYBDENA,
Molybdena is found in nature combined with
sulphur; forming the sulphuret of molybdena, which
resembles plumbago in some of its properties. This
mineral is of a bluish colour, more brilliant than
plumbago, and makes on paper a trace of a grey
tint. The metal has only been procured in small
grains, which do not differ much in their pro-
perties from the sulphuret. It combines with
oxygen, so as to form an acid called the molybdic
acid. The molyhdate of lead is a beautiful yellow
mineral.
The protoxide of molybdena is a tasteless pow-
der of a brown colour. Molybdena alloys with the
other metals,
TUNGSTEN.
A mineral called tungsten^ or ponderous stone,
affords a peculiar metal. This metal is capable of
being acidified, and when in this state it is joined
to lime, it forms the tungstate of lime.
The metal when pure is much like steel, and is
one of the hardest of the metals; a file can scarcely
make any impression on, it : it is also the heaviest,
OSMIUM. — IRIDIUM.— RHODIUM, 121
except gold and platinum. It is not used for any
purpose.
When heated in an open vessel it is oxidized,
and there are two oxides of tungsten. The pro-
toxide is of a brown colour, and when heated it
burns, and is converted into the peroxide^ which is
yellow, and has some of the properties of an acid,
being capable of combining with salifiable bases.
The mineral called wolfram is composed of
tungstic acid, manganese, iron, and tin.
OSMIUM.
This metal was discovered by Mr. Tennant, in
the ore of platina. The metal is of a dark grey
colour, and is oxidized when heated. Its oxide is
volatile, and has a peculiar smell. It is little known,
and has not been fused.
IRIDIUM.
This metal was also discovered by Mr. Tennant,
in the ore of platina. It is of a wliitish colour.
It is fusible, and malleable. It unites with oxygen,
and alloys with the metals. Its combinations are
little known.
RHODIUM.
Dr. WoUaston discovered this metal in the ore
of platina. It is very infusible, and forms malleable
alloys with the malleable metals. It unites to
oxygen like all the other metals, but is very little
known.
Igg PALI,AI)IUM.«- CADMIUM. -—TEJLiUmUM.
PALLADIUM.
This metal was discovered by Dr. WoUaston,
who found it in the ore of platina. Its colour is
of a duller white than platina ; it is malleable and
ductile, and for fusion it requires a stronger heat
than for gold. It is rather harder than iron.
It unites with sulphur, and is acted on by the
acids, but most readily by the nitro-muriatic.
It forms alloys with other metals, that with
gold has been usefully employed in astronomical
instruments, as it is hard, and does not tarnish.
CADMIUM.
This metal was discovered by M. Stromeyer, in
1817> in ores of zinc, particularly in brown fibrous
blende. It resembles tin, but is rather more fusi-
ble. It does not tarnish in the air.
It readily disolves in acids, but its salts are lit-
tle known. It is a rare metal, and not applied to
any use.
TELLURIUM.
This metal was discovered by Muller in 1782.
It is of a bluish w^hite colour, of considerable bril-
liancy. It is extremely brittle ; melts in a heat a
little greater than that required for lead. It is so
volatile that it may be distilled like mercury.
Its oxide has acid properties. It is formed by
burning the metal j a white smoke is disengaged,
which is the oxide. It may be also obtained by
TJTANIUM.'— CHROMIUM. 123
dissolving the metal in nitromuriatic acid, and di-
luting the solution with a large quantity of water.
Tellurium combines with hydrogen, and with it
forms a gaseous substance, called telluretted hy-
drogen.
This metal is scarce, and its combinations yet
little known.
TITANIUM.
This metal is rare. It was discovered in a
mineral, found in Cornwall, called menachanite.
It was afterwards procured from another mineral,
titanite, and some others. The metal when pure
is brittle, very infusible, of a brass or copper co-
lour, easily tarnishes in the air, and oxidizes by
heat. There appear to be three oxides of titanium,
the blue, the red, and the xvhite.
The ores of titanium are either pure crystallized
oxide, or the oxide united to iron, or to silex.
CHROMIUM.
This substance, little known in the metallic state,
is important on account of the fine pigments it
affords. It is capable of being acidified, and the
chromic acid forms salts. The beautiful mineral
called red-lead of Siberia, is a chromate of lead.
This is now artificially prepared, and is a very va-
luable and beautiful yellow pigment. The chro-
mic acid also unites to iron, the chromate of iron
being found native ; and it is from this that the
chromic acid is procured and united to lead, to
form the chromate of lead. Chromate of iron is,
therefore, much sought after, and is found in
greatest abundance in America, from whence our
colour-makers chiefly procure it.
124 URANIUM. —COLUMBIUM.— CERIUM,
The pure metal is of a tin colour ; it is very
brittle, and is said to be magnetic. It is very in-
fusible, and is not altered by the air, though when
heated it is converted to an oxide.
Besides its acid, it seems to combine with oxy-
gen in two other proportions, forming the green
and hroTdon oxides.
URANIUM.
This metal was discovered by Werner, in a mi-
neral called peclihlende, a blackish mineral re-
sembling pitch.
Metallic uranium is brittle, and veiy infusible.
It is of a grey colour. It is obtained with extreme
difficulty, and little known.
Its oxide is greenish-yellow, and is found native,
resembling green mica, and also in an earthy
state.
COLUMBIUM.
This metal was discovered by Mr. Hatchet in
analyzing an ore from North America. It has
since been found in the minerals called tantalite
and yttro-tantalite. The metal has been procured
by Berzelius. It is of an iron colour, hard and
brittle, and passes into an oxide at a red heat.
Its oxide is white. Its combinations are little
known ; but it is one of the acidifiable metals.
CERIUM,
This metal was lately discovered by Berzelius,
in a mineral which has been called cerite. The
characters of the metal are imperfectly known, as
SELENIUM. — VEGETABLE SUBSTANCES. 125
it has been scarcely seen. The oxide of cerium
(cerite) is found native. There appear to be two
oxides, the white and the 7'ed.
SELENIUM.
Selenium is a metal lately discovered by Berze-
lius in the sulphur of Fahhun, in Sweden. Its
metallic lustre is considerable, and colour grey.
It easily fuses and volatilizes before the blow-pipe,
with a smell like horse-raddish. It alloys with the
metals. It dissolves in nitric acid, and forms with
it a substance which is considered as a new acid,
selenic acidy which unites with alkalies, forming se^
leniates»
VEGETABLE SUBSTANCES.
Animals and vegetables differ essentially from
minerals, in the two first possessing life and various
organs fit for maintaining it, which is called organic
structure. Through these organs, various juices and
fluids circulate internally, and thus occasion the
growth of the animal or plant. In mineral bo-
dies this is pot the case j they increase in size only
by successive portions of matter adhering to the
outside^ nor is there any internal motion.
The principal ingredients of ail vegetables are,
oxygen, hydrogen, and carbon : sometimes they
contain also a little nitrogen, and other elementary
substances ; and although these elements are few,
yet, by many varieties in their proportions and
modes of combinations, a great quantity of proxi-
mate constituents are produced.
126 VEGETABLE SUBSTANCES.
Vegetable substances may be decomposed, or
separated into their elementary principles by various
means ; by heats, by acids, and by fermentation :
some of these processes occasion not only decom-
position, but also new combinations of the elements
that did not exist in the living bodies.
The principal substances of which all vegetables
consist are.
Mucilage, or gum,
Woody fibre,
Sugar,
Colouring matter,
Fecula,
Tannin,
Gluten,
Wax,
Fixed oil,
Camphor,
Volatile oil.
Bitter principle,
Resin,
Narcotic principle.
Caoutchouc,
Vegetable acids.
Mucilage^ or gum. — Various parts of vegetables
impart to water, particularly if boiled with them,
a certain viscous consistency : the substance so
dissolved is called mucilage. Some trees suffer
their mucilage to transude, either spontaneously
or by incisions made in them. AVhen it has
become concrete by drying in the air, it is called
gum.
Gum is soluble in water, but not in oils or al-
kohol, the latter of which precipitates it from its
solution in water. It is insipid ; it does not un-
dergo any change by exposure to the air when dry.
The gums of different trees differ considerably in
their properties. Gum arable may be considered
as a very pure gum. Cherry-tree gum and gum
tragacanth do not dissolve in cold water ; but dis-
solve in boiling water, and, on cooling, assume the
state of a jelly.
VEGETABLE SUBSTANCES. 127
Gum consists of carbon, oxygen, and hydrogen.
Sugar. — The sugar in common use is extracted
from a cane that grows only in warm climates, called
the sugar-cane ; but it may also be procured from
all sweet vegetables. The American maple-tree
affords a great deal of sugar, and this useful sub-
stance has been made from the beet-root, car-
rots, &c.
All sugars consist of carbon, oxygen, and hydro-
gen ; but it appears that sugar from the cane
contains more carbon than other sugars. That
obtained from some vegetables will not crystallize.
Sugar is first prepared in the countries where it is
grown, by boiling the juice and evaporating ; one
part of the juice crystallizes, and forms the raw or
muscovado sugar ; the other part, the molasses or
treacle, will not crystallize. The raw sugar when
brought to this country is re-dissolved and crystal-
lized again, which is called refining, by which the
loaf-sugar is made. To whiten it completely, clay
is put upon the tops of the conical pots in which
the sugar has granulated, which allows water to
percolate through, and thus drain off the last re-
mains of the molasses. This is called claying the
sugars.
Fecula, or starch. — This substance is contained
in many seeds and roots. It is separated by bruising
the vegetables containing it in water, and stirring
them together. The fecula separates in the water,
making it appear turbid. The white fluid is pour-
ed off and suffered to settle ; the starch subsides
to the bottom. Starch is made mostly from wheat;
it is also made form potatoes. Starch is a white
substance, insoluble in cold water, but soluble
in warm. Its solution is gelatinous, and when
solid it resembles gum : this, when dry, is a com-
128 VEGETABLE SUBSTANCES.
pound of starch and water. Starch is not soluble
in alkohol.
In the process of converting grain into malty the
starch or fecula is changed into sugar. It may
also be converted into sugar by boiling it with
diluted sulphuric acid.
Starch consists of carbon, oxygen, and hydrogen.
Gluten. — This principle is found in various vege-
table juices, but most abundantly in wheat flour. It is
separated from it by washing, with a stream of water,
a paste made of flour and water, at the same time
kneading it between the fingers. The water car-
ries off the starch gradually, leaving the gluten be-
hind. Gluten is insoluble in water, and is elastic
like elastic gum. It has no taste, and, when dried,
becomes hard and brittle. It considerably resem-
bles animal gluten, furnishing ammonia by distil-
lation.
Fixed oil. — This is obtained by pressure from
certain seeds and fruits, as the olive, linseed, rape
seed, almond, &c. The fixed oils differ much ;
some being nearly solid, are called vegetable
butters. When expressed, they are generally mixed
with some mucilage, which occasions them to turn
rancid. They may be deprived of their colour by
charcoal. Fixed oils dissolve sulphur, and then
form balsams. They also dissolve phosphorus.
Fixed oils are very combustible, and, when
strongly heated, yield olifiant and carburetted hy-
drogen gases.
They form soaps by being combined with alkali.
The best soaps are made of olive oil and soda ; but
common soaps are made with the animal oils and
fat.
Transparent soap is made by dissolving soap in
alkohol, and then concentrating the solution whicli
VEGETABLE SUBSTANCES. 129
is of a gelatinous consistence, by distilling off the
alkohol.
Fixed oils are mucli used for painting, as they
are of a drying nature : they are rendered still
more drying by boiling them with the oxides of
metals, as litharge.
Volatile oil. — This is also called essential oil.
Many vegetables afford essential oil by expression,
or by distillation, When dissolved in water they
constitute perfumed essences and distilled waters.
They have much odour and taste. They are in-
flammable. They are volatilized by a gentle heat,
and evaporate entirely when pure so as to leave no
trace. The chief essential oils are, the oils of tur-
pentine, spike, cloves, oranges, lemons, lavender,
&c. Many of them bear a high price.
Resin. — The resins are an important class of
vegetable substances from their application in the
arts. They are very numerous, and often exude
spontaneously from trees. Common resin is obtained
from the^r ; a juice exudes from this tree, which is
common turpentine: this consists of the oil of turpen-
tine and resin. When the essential oil is separated
by distillation, the resin remains. Mastich is a resin
obtained from a tree that grows in Turkey. San-
darach is the resin of a tree in Barbary. Copal is
a resin from a tree that grows in America, and is
a very valuable substance for varnishes. Lac is a
resin made by an insect in the East Indies. It is
very useful in varnishes, and in sealing-wax. Am-
ber is a substance resembling in its properties the
resins, but it is only found in the earth, or washed
out and driven on the shores. All the resins are
insoluble in water, but soluble in alkohol, especially
when assisted by heat. The greater number are
soluble in the essential oils, and some are so in the
VOL, II. K
ISO VEGETABLE S¥BSTANCES.
fixed oils. They are also dissolved by alkaline
]ys, and by the acids. Resins consist of oxygen,
carbon, and hydrogen ; and they are supposed to
be volatile oils saturated with oxygen.
Bitumen is a substance having some analogy
witli oils and resins, although differing in its consti-
tuents, and being also a mineral body. Pure bitu-
men is called naphtha, which is transparent, highly
inflammable, volatile, of a pungent odour ; it is found
in certain wells, and there are springs of it in several
parts of the world. When naphtha is exposed to
the air, it thickens, and becomes dark coloured; it is
then called j9e/ro/ez^w, which is procured in the same
manner, and is used for burning in lamps. Maltha
or mineral pitch is a still farther thickened bitumen,
and when it has become solid it is called asphaltum.
Caoutchouc. — This is the substance usually
known by the name of Indian ri(hbcr, and- some-
times elastic gum. It was first brought from South
America. It exudes as a milky juice from a tree,
which thickens and hardens by exposure to the
air. The natives form it into bottles by coverina:
balls of clay with this juice ; the clay is afterwards
washed out after the caoutchouc is solid. When
caoutchouc is pure, it is white, the black colour
being owing to the smoke used in drying it. This
substance is extremely elastic. It is perfectly inso-
luble in water, but it may be softened by boihng, ;
so that its edges may be united together. It is not (
soluble in alkohol : but it is soluble in ether j and
when the ether is evaporated, the caoutchouc re- I
mains unaltered in its properties : by this means
tubes and other instruments might be made of it, \
but the method would be too expensive. It is so-
luble in some of the fixed and essential oils, as in
spermaceti and in oil of cajeput. if
I
I
VEGETABLE SUBSTANCES. 131
Woody fibre. — When a piece of wood has been
boiled in water and in alkohol, until the soluble sub-
stances have been extracted from it, what remains
insoluble is the woody fibre, or lignin^ which is the
basis oi wood, and consists of long fibres, having
a considerable degree of transparency, without
taste, and unalterable by the air. It is insoluble in
water and alkohol. It is very inflammable ; and,
when distilled in a close vessel, yields an acid sub-
stance formerly thought to be a distinct acid called
the pyro-ligneous, but now known to be the acetic
acid with an empyreumatic oil. Pure acetic acid or
vinegar is now made from wood by distillation.
Wood consists of oxygen, carbon, and hydrogen j
when burned, the carbon remains, constituting
charcoal.
Colouring matter. — The colours of vegetables
are owing to peculiar matters, which are extremely
numerous, and but little known. Many of them
are used as dyes and pigments. The extraction of
colouring matters from vegetables, and fixing them
on cloths, constitute the arts of dyeing and calico-
printing (which see). The colouring matters
sometimes are inherent in gums, sometimes in
resins, sometimes in fecula ; consequently they
require different chemical agents for their solution.
Tannin. — This principle is so called because it
is employed in the art of tanning leather. It is
also called the astringent principle. It is found
abundantly in the barks of several trees, particu-
larly the oak, and also in certahi seeds. The gall-
nut and grape-seeds afford very pure tannin ; and
a substance called catechu^ from India, consists
chiefly of it. Tannin is distinguished by its
forming a precipitate with glue, or isinglass. This
precipitate is insoluble in water, and is that wliich
.132 VEGETABLE SUBSTANCES.
is formed when skins are tanned and made into
leathe7\
Wax. — This substance appears to be formed by
bees, by some animal process. It is also a vege-
table substance, for the polish or varnish of leaves
is owing to a coating of wax ; and in some vege-
tables in Brazil wax exists in considerable quan-
tity; Wax is insoluble in water, but sparingly
dissolved by boiling alkohol. It is dissolved rea-
dily by the fixed oils, and then forms cerates and
ointments. Wax contains a large proportion of
carbon, with hydrogen and oxygen.
Camphor. — This substance is brought chiefly
from Japan, and is distilled from a species of laurel.
It is white and semitransparent ; it is very inflam-
mable, soluble in alkohol, and sparingly so in water.
It is very volatile, and capable of converting into
an acid, called the camphoric acid, which form
' neutral salts called camphorates. Camphor resem-
bles essential oil in many of its properties.
Bitter principle. — It is supposed that this is a
peculiar principle. It exists in many vegetables,
particularly in quassia, gentian, hop, &c. When
extracted, it is of a brownish yellow colour, and
brittle when dry. Its taste is very bitter. It is
soluble in water and alkohol. A variety of it is
supposed to exist in unroasted coflfee.
Narcotic priiiciple. — This has lately been called
morphine, and is found most abundantly in opium,
which consists of this together with several of the
principles which have been just described. It is a
violent poison when taken internally. When pure
it is white, without taste or smell. It is soluble in
boiling alkahol, but is scarcely acted upon by water.
From the rapid progress of chemistry, many
other vegetable substances are considered as pe-
VEGETABLE SUBSTANCE^. 133
culiar principles ; but it would exceed the bounds
of this work to describe them all in detail. The chief
amono- them are saber, or a peculiar substance found
in cork j asparagin, found in asparagus ; medullinj
from the pith of the sunflower ; fungin, the fleshy
part of mushrooms, &c.
Vegetables also contain several acids ready
formed. Vegetable and animal acids differ from
the others essentially. They always contain car-
bon and hydrogen : some of them contain azote,
and generally, though perhaps not always, oxygen.
They do not seem capable of combining with dif-
ferent proportions of oxygen only, but whenever
the quantity of this principle changes, that of the
rest changes also.
Tartaric acid. — Tartar , or cream of tartar^ is a
substance found in an impure state, incrusted^on
the bottom and sides of wine casks : when purified
by solution and filtration, it is sold for use. This
salt, which is soluble in water, consists of tartaric
acid and potash ; it is therefore tartrate of potash.
Tartaric acid when crystallized is imperfectly trans-
parent, white, and does not deliquesce in the aii«
It is soluble in water. It combines with alcalies,
earths, and metallic oxides, and forms tartrates.
Ojcalic acid, so called from being first obtained
from oxalis acitosella, or wood-sorrell. It is also
called the acid of sugar, because obtained from
sugar by the nitric acid. It is proper that every
one should know that oxalic acid is a deadly poison,
and that many persons have lost their lives by
mistaking it for Epsom salts, which it resembles.
It IS much employed for cleaning boot-tops and
leather, and also by the calico-printers.
Malic acid was first found in the juice of apples.
It exists also in many other vegetables. This acid
K S
154 FERMENTATION.
is very sour, and does not crystallize ; it forms
salts with many of the metallic oxides.
Gallic acid. — Tliis acid is found in gall-nuts.
It crystallizes, and forms whitish crystals, of a sour
taste and peculiar smell. When gallic acid is put
into a solution containing iron, a black precipitate
appears. The base of ink is iron thus precipi-
tated. To produce good black ink, infuse one
pound of powdered gall-nuts for four hours,
without boiling, in common water, with six ounces
of gum-arabic, and six ounces of sulphate of iron.
With gold, gallic acid forms a brown precipitate j
with silver, a grey ; with mercury, an orange; with
copper, a brown ; and with lead, a wliite.
Citric acid is procured from the juice of lemons
and other fruits. It is capable of crystallizing.
Its crystals are soluble in water, and very sour. It
forms citrates with the earths, alkalies, and metals.
It is much used in calico-printing. It is also used
for discharging spots of ink from linen.
Benzoic acid is obtained from gum-benzoin, or
benjamin. It is a crystallizable acid. The com-
pounds which it forms are called benzoates,
Kinic acid is found in Peruvian bark.
FERMENTATION.
If mucilagi-nous saccharine vegetable substances
be subjected to the action of water and heat, (from
60 to 70 tleg. Fahr.) they experience, in a very
short time, a very striking change. An internal
commotion takes place, the mass grows turbid, a
large quantity of air-bubbles, consisting of carbonic
acid gas, are disengaged, which, on account of the
viscidity of the matter in which they are inclosed,
form a stratum on the surface of the fluid, known
FERMENTATION. 155
by the name of yeast. After a time these appear-
ances cease, the fermented liquor becomes clear
and transparent, and no more gas is discharged.
The liquor now has lost its sweetness and viscidity,
and has acquired the vinous taste and intoxicating
quality. Sugar appears to be essential to this pro-
cess J and all mucilaginous substances containing
sugar are capable of this fermentation, which is
called the vinous.
Wine is made in this manner from the juice of
the grape ; if the fermentation be checked when
at its height, by excluding the air, the wine begins
to ferment anew, and effervesces when again ex-
posed to the air. The sparkling wines, as Cham^
pagne, are prepared in this manner, and hence
should be considered as imperfect wines.
To prepare vinous liquors from grain or corn, it
must first be converted into maU^ by steeping it in
water, and then exposing it to the air, turning it
frequently over j by this process, the gluten of
which the germ consists is separated, and the
fecula is converted into sugar by the germination
of the seed.
Beer is made by boiling the malt in water, which
produces a sweet liquor called tvoi^t ; this is con-
verted into beer by fermentation and the addition
of hops, which furnish a bitter substance.
Wine, beer, and all fermented liquors, owe their
intoxicating qualities to a peculiar substance which
they contain, and which is the produce of fermen-
tation alone. . This substance is a fluid called alko-
hoi, or spirit of m7ie, and may be separated in a
pure state by distillation. When first obtained it
is mixed with a quantity of water, but if it be re-
distilled, it is obtained very pure, and is then called
rectified alkohol. Alkohol is of a strong heating
K 4
lS6 FERMENTATION*
taste, of a peculiar penetrating odour, and it is
very inflammable and volatile. It dissolves resins,
essential oils, camphor, sulphur, phosphorus, &c.
It is composed of hydrogen, carbon, and a small
quantity of oxygen.
Strong acids and alkoliol have a considerable
action on each other, and this produces ether^ which
is a fluid still more highly volatile, inflammable,
and odorous. Nitric acid with alkohol produces
nitric ether ^ and sulphuric acid in the same way
produces sulphuric ether.
When wine, or any fermented or vinous liquor
is exposed to a heat, from 75'^ to 85S Fahr., and
access of air is permitted, the fluid becomes turbid,
and a new change of principles takes place. It
loses its taste and smell, it becomes sour, and is
converted into vinegar, or acetous acid. Though
vinegar is chiefly prepared from fluids which have
undergone the vinous fermentation, yet this is not
necessary to the production of vinegar, for simple
mucilage is capable of passing into the state of
acetous fermentation. When the saccharine prin-
ciple predominates in any substance exposed to
the necessary conditions of fermentation, alkohol
is produced ; when mucilage is most abundant,
vinegar or acetous acid is the product j and when
gluten is predominant, ammonia will be discovered,
and putrefaction will take place.
Common vinegar may be purified, or concen
trated by distillation, and it is then called distilled
vinegar. This, however, still consists of the acetic
acid and water. To free the acid from the water,
distilled vinegar is saturated with some metallic
oxide, and an acetate is thus formed. The acetate
is then heated red hot in a retort, by which it is
decomposed, and the acetic acid passes over pure.
ANIMAL SUBSTANCES. 137
Acetate of copper or verdigris^ and likewise ace-
tate of leady are used for this purpose. Acetic
acid is very pungent and caustic. It is very vola-
tile, and combines with the metals, earths, and
alkalies.
This acid may also be obtained from wood, by
subjecting it to distillation in a retort. In this state
it is very impure, being combined with a quantity
of empyreumatic oil. This was formerly called pi/-
roligneous acid. When separated from impurities
it is essentially the same with vinegar, and is now
employed for the same purpose.
The last change, or final decomposition that
vegetables undergo, is called the putrefactive fer-
mentation^ OY putrefaction. Without moisture, heat,
and a due access of air, this does not take place.
By this vegetables are resolved into their consti-
tuent principles, and ammonia is formed.
ANIMAL SUBSTANCES.
The elementary principles of animal substances
are nearly the same with those of vegetables, but
the former contain more nitrogen and phosphorus,
and the latter more carbon and hydrogen.
The proximate constituent parts of animal sub-
stances are the following :
Gelatine^ or animal jelly, is very generally dis-
persed through all the parts of animals, even in
bones, but exists in the greatest quantity in the
tendons, membranes, and the skin. It is a viscid
substance, very soluble in warm water, but not in
alkohol ; insipid, and without smell ; when cold, it
congeals into a cohesive, tremulous substance. It
forms the basis of soups, broths, &c. and imparts to
138 ANIMAL SUBSTANCES,
them tlieir nutritious qualities. \VTien evaporated
to dryness, it forms poi^table soup, size, ghie, &c.
The union of this latter substance in the skin with
tannin constitutes leather. Isinglass is gelatine
procured from certain parts of several fish, particu-
larly the sturgeon. The tendons and membranes of
the body are chiefly gelatine.
Fibrin, or animal Jibre, forms the basis of the
niusctdar, or fleshy parts of animals. It is there
combined with albumen, and remains with it after
all the soluble parts of the flesh have been separated
by water. It may also be obtained from blood, by
washing the clot or coagulum in water, till a white
fibrous matter remains. Fibrin is not soluble in
cold watei% but is very slightly so in boiling water.
It is soluble in acids and alkalies, and by its union
with the latter a soap is formed. Chaptal em-
ployed this joroperty to make a soap from wool.
It is very analogous to vegetable gluten.
Albinnen is the principal constituent of the serum
of blood, and is also called coagidable lymijh. The
white of eggs consists almost entirely of albumen.
It is miscible with cold water, but is coagulated by
heat, which forms the best test of its presence.
It is also coagulated by acids and alkohol.
Mucus. — This substance in animals appears in-
tended to lubricate or smooth certain parts of the
body, and seems very analogous to a solution of
gum. However, Dr. Bostock has shown that it
diflfers from gelatine, as it cannot in cold water be
brought to assume the gelatinous state. Tannin
precipitates gelatine, but not mucus, whereas sub-
acetate of lead, (extract of Goulard,) forms a preci-
pitate with mucus, but not with gelatine. Mucus
is found in saliva, tears, in the intestines, joints, &c.
ANIMAL SUBSTANCES. IS^
Oil.'— Animal oils are fat, tallow, butter, &c.
They are mostly solid at the usual temperature.
They may be rendered fluid by heat. Oil is ob-
tained in great quantities from certain fish, parti-
cularly the whale, seal, &c. and fish oil continues
fluid. It is very similar to vegetable oil in its other
properties. Spermaceti somewhat resembles wax,
and is obtained from the head of a species of whale.
Animal fibre may be converted into a substance
like spermaceti by treatment with the nitric acid,
or by exposing it to a current of running water for
several months. This has been called adipoeire.
It has been shown lately that fat is a compound
body, consisting of a substance solid and much like
wax, which has been called stearin^ and a fluid oil
called elain.
Milk is a substance secreted by certain animals
for the nourishment of their young. As is well
known, milk on standing for a day throws up cream
to the surface. Cream has mucli of the properties
of an oil, and when agitated by churning, butter is
separated from it. If milk stands until it becomes
sour, it separates into a coagulum and a whey.
This change may be more completely effected by
adding to the milk a small quantity of certain sub-
stances, as acids, or rennet^ procured by boiling in
water the inner coat of the stomachy of a calf.
The coagulum is thus made more solid, and when
pressed and dried it forms cheese.
In animal bodies there are also found several pe-'
culiar acids.
The lactic acid is found in sour whey. It com-
bines with the earths and alkalies, forming salts
called lactates. It resembles much the acetic acid.
The uric acid is found in urine. The substance
voided with the urine called gravel, and also those
140 ANIMAL SUBSTANCES.
stones formed in the bladder called calculi, are
almost entirely composed of nric acid. This acid,
however, exists in urine even in its most healthy
state.
The amniotic acid is found in the liquor of the
amnios of a cow. It separates in white crystals.
The saccho-lactic acid is formed by acting on su-
gar of milk, or on gum by the nitric acid. It
forms salts called saccho-lactates.
The sehacic acid is procured from animal fat. It
becomes solid, is of a white colour, with a taste
slightly acid.
The Prussic acid has been described, p. under
the name of the hydrocyanic acid.
The formic acid is an acid procured from ants.
Animal resins. — Peculiar tesins have been found
in certain animal substances, as in the bile, amber-
gris, &c.
Animal sugar is found in milk, also in the urine
in certain diseases. It is similar to common sugar.
" Blood, when suffered to rest, separates into two
parts J the one a coagulum or clot, called the
crassamentum ; the other, a fluid called the serum.
The crassamentum consists of fibrin mixed with al-
bumen and colouring matter. The colouring part
of blood consists of extremely minute globules of
a red colour, which float in the serum, and may be
seen by the microscope. The red colour of blood has
been supposed to be owing to iron which was oxy-
dated by the air in the lungs, but this theory is
now rendered questionable. The serum is com-
posed of albumen, and also contains a small por-
tion of alkali and other substances. It is coagu-
lated by heat, the acids, and alkohol.
Bone is composed of gelatine, another substance
which seems t5 be analogous to cartilage or coa-
ANIMAL SUBSTANCES. 141
gulated albumen, an oil, or marrow, and phosphate
and carbonate of lime, besides other matters in
minute portions.
Teeth are composed of similar ingredients.
Shells contain a greater proportion of carbonate
of hme.
Horns, nails, hoofs, and quills are chiefly gelatine
and albumen.
Besides the animal substances above enumerated,
there are various matters secreted or formed by cer-
tain organs in the body, as saliva, the gastric juice,
the bile, thejluid ofi^erspiration, kc, the nature of
which is not yet thoroughly known.
The examination of animal substances, called
animal chemistry, is one of the most difficult, as
well as one of the most important, branches of the
science ; and a wide field is yet open for research.
When animal bodies are deprived of the vital
principle, and are exposed to the air, they undergo
a speedy decomposition called putrefaction. By
this they are resolved partly into their elementary
principles, and some of these form new compounds.
The first change is observed by the bodies altering
in their colour, losing their elasticity, and by their
giving out a very fetid and noxious sm.ell. The
greater part, in time, assumes a gaseous form, and
nothing remahis but a small quantity of earths and
salts.
One of the greatest improvements in chemistry
has been that made in its nomenclature, which we
owe chiefly to the French chemists. As the former
names of many substances differ so entirely from
those at present employed, that, without some
assistance, many of the old writers on chemistry
are not now" intelligible to those acquainted only
with the modern nomenclature, a list is subjoined
142
NOMENCLATURE OFJ CHEMISTRY.
of the terms which most generally occur in old
books on this subject, together with those which
are now adopted instead of them.
}
Old Names arranged
Alphabetically.
Acetous salts
Acid of vitriol, phlogisticated
— of alum
— of vitriol
— of vitriolic
— of sulphur
— of nitre, phlogisticated
— of nitre, dephlo-
gisticated
— of saltpetre
— of sea salt!
— marine - j"
— aerial - "]
— of chalk I
— cretaceous [>• -
— of charcoal |
— raephitic J
— of spar or fluor ")
— sparry - |
— of borax
— of arsenic
— of tungsten |
— of wolfram J'
— of molybdena
— of apples
— of sugar n
— saccharic J
— of lemons
— of tartar
— of benzoin
— of galls
— of amber
— of ants
— of phosphorus phio- ")
gisticated - j
— of phosphorus de- ")
phlogisticated J
New Names.
Acetates
Sulphureous acid
Sulphuric acid
Nitrous acid
Nitric acid
Muriatic acid
Carbonic acid
Fluoric acid
Boracic acid
Arsenic acid
Tungstic acid
Molybdic acid
Malic acid
Oxalic acid
Citric acid
Tartareous acid
Benzoic acid
Gallic acid
Succinic acid
Formic acid
Phosphorus acid
Phosphoric acid
NOMENCLATURE OF CHEMISTRY.
14.3
n
Old Names arranged
Alphabetically,
Acid of fat \
— sedative /
— of lac -
— ofmilk
— of the sugar of milk
Air -
— dephlogisticated'
— empyreal
— vital
— pure
— impure, or vitiated")
— burnt - - >
— phlogisticated J
— inflammable
— marine acid
— dephlogisticated)
— marine acid j
— hepatic - - 7
— fetid of sulphur 3
Air fixed - >
— sohd of Hales j
— alkaline
Alkalies, fixed
■ volatile
— concrete volatile
caustic
effervescent, ae- \
rated, or mild J
vegetable
mineral or marine
Prussian -
Alum
Antimony, crude
Aqua fortis -
regia -
ammonia pura
Argil, or argillaceous earth
Bezoar mineral
Black lead -
Borax
Butters of the metals
Calces, metallic
Ceruse
Nexv Names.
- Sebacic acid
- Laccic acid
- Lactic acid
- Saccho-lactic acid
- Gas
- Oxygen gas
- Nitrogen, azote, or azotic gas
- Hydrogen gas
- Muriatic acid gas
- Oxygenated muriatic acid gas,
or chlorine
- Sulphureted hydrogen
- Carbonic acid gas
- Ammoniacal gas
- Potash and soda
- Ammonia
- Carbonate of ammonia
- Pure alkalies
- Alkaline carbonates
- Potass
- Soda
- Prussiate of potash
- Sulphate of alumine and potash
Svdphuret of antimony
- Nitric acid of commerce
- Nitro-muriatic acid
Ammonia
- Alumine, or alumina
- Oxide of antimony
- Plumbago
- Borate of soda
- Muriates of the metals
- Metallic oxides
» Carbonate of lead
144<
NOMENCLATURE OF CHEMISTRY.
Old Names arranged
Alphabetically.
Ceruse of antimony -
Charcoal, pure
Colcothar of vitriol -
Copper, acetated
Copperas, green
• blue
Cream of tartar
Earth, calcareous
aluminous
siliceous
' ponderous
magnesian, or muriatic
Emetic tartar
Essences . - -
Ethiops, martial
• mineral
Flowers, metallic
of sulphur -
Fluors . - -
Hepars . - -
Heat, latent
Kermes mineral
Lapis infernalis
Leys
Liquor sllicum 1
of flints J
Litharge
Liver of sulphur, alkaline
calcareous
Luna cornea
Magistery of bismuth
Magnesia alba ")
• aerated j
■ black
Masticot
Mephitis
Minium
Mother waters
Nitre, or saltpetre -
Neix Names.
White oxide of antimony
Carbon
S Red oxide of iron by the sul-
( phuric acid
Acetate of copper
Sulphate of iron
of copper
Acidulous tartrate of potash
Lime
Alumina, or alumina
. Silex
Barytes
Magnesia
Antimoniated tartrate of potash
Volatile oils
Black oxide of iron
J Black sulphureted oxide of
\ mercury
Sublimated metallic oxides
Sublimated sulphur
Fluates
Sulphurets
Caloric
f Red sulphureted oxide of an-
\ timony
Fused nitrate of silver
Solutions of alkalies
Solution of siliceous potash
J Semivitreous oxide of lead or
\ litharge
Sulphuret of potash
of lime
Muriate of silver
(Oxide of bismuth by the nitric
I acid
Carbonate of magnesia '
Black oxide of manganese
Yellow oxide of lead -
■ Nitrogen gas
• Red oxide of lead
• Saline residues
■ Nitrate of potass
NOMENCLATURE OF CHEMISTRY.
145
Old Names arranged
Alphabetically.
Nitres
Oils, fat -
• etherial
of tartar per deliquium
Phlogiston -
Phosphoric salts
Precipitate, red
■ per se
Principle, astringent
■ tanning -
— — acidifying
inflammable
Pyrites of copper
Pyrites martial
Realgar
Reguliis of the metals
Rust of iron
Saffron of Mars
Sal ammoniac
— polychrest
Salt, common or sea
— febrifuge of Sylvius
— fusible of urine
— Glauber's
— Epsom -
— of sorrel
— of wormwood -
— vegetable
Saltpetre
Selinite
Spar, calcareous
fluor -
ponderous
Spirit, ardent "i
of wine 3
— — of nitre
of salt
Nex'o Names.
' Nitrates
. Fixed oil
■ Essential oils
A solution of potash
f A principle imagined by Stalil,
\ but now not admitted
. Phosphates
f Red oxide of mercury by the
\ nitric acid
- Red oxide of mercury by fire
- Gallic acid
- Tannin
- Oxygen
- See Phlogiston
- Copper pyrites
rlron pyrites, or sulphuret of
"1 iron
("Red sulphuretted oxide of
\ arsenic
- The metals in a pure state
- Oxide of iron
- Oxide of iron
- Muriate of ammonia
- Sulphate of potash
- Muriate of soda
- Muriate of potash
- Phosphate of soda
- Sulphate of soda
of magnesia
- Acidulous oxalate of potash
- Carbonate of potash
- Tartrite of potash
- Nitrate of potash
- Sulphate of lime
- Crystallized carbonate of lime
- Fluate of lime
- Sulphate of barytea
- Alkohol
- Nitric acid
- Nitrous acid
- Muriatic acid
VOL. II.
146
NOMENCLATURE OF CHEMISTRY.
Old Names arranged
Alphabetically.
Spirit of sal ammoniac
of vitriol
Spiritus rector
Sublimate, corrosive
Sugar of lead
Tartar
emetic
vitriolated
Tartars
Tinctures, spirituous
Turbeth mineral
Vinegar, distilled")
radical j
Vitriols
Vitriol, blue
green
— — white
Water acidulated
"^ hepatic
Netu Names.
• Ammonia
Sulphuric acid
• Aroma
- Muriate of mercury
■ Acetate of lead
■ Acidulous tartrite of potash
Antimoniated tartrite of potash
■ Sulphate of potash
■ Tartrites
Resins dissolved in alkohol
J Yellow oxide of mercury by the
\ sulphuric acid
Acetic acid
■ Sulphates
. Sulphate of copper
of iron
of zinc
c Water impregnated with car-
\ bonic acid gas
{Water impregnated with sul-
phuretted hydrogen
147
MANUFACTURES AND ARTS.
The modern sciences, and particul-ajy cbemjstjy,
have been of late successfully applied to the im-
provement of several of the useful arts j and some,
in consequence, have undergone almost an entire
change. Of the principles of some of them we
propose to give a brief description.
MAKING BREAD.
Scarcely any nation exists, in which the use of
bread is entirely unknown, or something as a sub-
stitute for it ; a dry food appearing to be neces-
sary to promote the secretion of saliva, in the pro-
cess of mastication.
In Lapland, where they have no corn, they make
a kind of bread from dried fish, and of the inner rind
of the bark of the pine. In some parts of xlmerica,
they use, for this purpose, casava, the root of a
plant which is poisonous till it is rendered whole-
some by the extraction of its acrid juice. In the
South Sea islands, the bread-fruit tree affords the
natives a substance resembling bread.
From time immemorial, the farinaceous seeds
have been employed as food, and they are the most
nutritive of all the vegetables. Few of the alimen-
tary substances are used by man in a raw ana
crude state; almost all undergo some preparation,
by which they are rendered more easy of diges-
tion, or are more palatable. The application of
L ^
148 MAKING BREAD.
heat generally effects considerable changes in tlie
different principles of which they are composed.
Thus, bread from wheat is no longer capable of
forming a paste with water, such as can be made
with flour ; nor can starch, and gluten, elements
existing in flour, be obtained from it after it has
been baked in bread. The alteration in potatoes
by the culinary process is even more considerable.
The farinaceous vegetables used for making
bread, are chiefly wheat, barley, oats, rye, buck
wheat, maize, beans, pease, rice, potatoes, &c. In
times of scarcity, other substances have been used,
as acorns, chesnuts, &c.
Of all these wheat is found to afford the best
bread, and we shall begin by describing it. Wheat
flour, when analysed, is found to consist of —
1. Gluten. 2. Fecula, or starch, 3. Saccharine
matter, or mucilage.
The gluten is very elastic, of a greyish white
colour, and when drawn out to its fullest extent,
has the appearance of animal membrane. In this
state, it adheres to many bodies, and forms a very
tenacious glue, which has been used for mending
broken porcelain. It is insoluble in water, alkohol,
ether, or oil ; and, in many of its properties, it re-
sembles animal substances.
The Jecula is a delicate white powder, soft to the
touch, scarcely sensible to the taste, almost inso-
luble in cold water, but soluble in warm water.
The saccharine part is a sugar similar to what is
contained in other vegetables.
These three constituent principles are easily
separated from each other in the following manner.
Knead some flour with water, and let a stream of
water constantly flow over it. The fecula, or
starch, will be carried off' by the water, and will
MAKING BREAD. 149
fall to the bottom of the vessel where it is collected;
the siiffar will be held in solution in the water em-
ployed, and the gluten will remain alone.
There are three sorts of bread in general use,
prepared from wheat flour : 1. Unleavened
bread. 2. Leavened bread. S. Bread made with
yeast.
Unleavened Bread.
When flour is kneaded with water, it forms a
tough adhesive paste, containing the constituent
principles of flour, with little or no alteration, and
not easily digested by the stomach.
When formed into cakes, and baked by heat, the
gluten, and probably the starch, undergo a con-
siderable change, and the compound is rendered
more easy of digestion.
Bread made in this manner, without any addition,
is called unleavened bread. It is not porous, but
solid and heavy.
This is, no doubt, the most ancient method of
preparing bread, and it is still used in many coun-
tries. The oat cakes, and barley bread, used in
Scotland, and the north of England, are of this
kind ; so are also biscuits of all kinds.
Unleavened bread is also used by the Jews
during the Passover.
OfLeave7ied Bread.
When flour is kneaded with water, it is called
dough ; and when this is kept in a warm place, it
swells up, becomes spongy, and is filled with air-
bubbles ; it disengages at length an acidulous and
spiritous smell, tastes sour, and in this st3>t,e is called
leaven, .7.: .
Here the saccharine part has been converted
into ardent spirit, the mucilage tends to acidity,
L 3
||J0 MAKING BREAD.
and the gluten probably verges towards a state of
putridity. By this incessant fermentation, the
mass is rendered more digestible and light, that
is, it becomes much more porous by the disengage-
ment of elastic fluid, which separates its parts from
each other, and much enlarges its bulk. The
operation of baking puts a stop to this process, by
evaporating a great part of the moisture, which
favours the chemical attractions, and probably also
by further changing the nature of the component
parts. Bread, however, in this state, will not pos-
sess the requisite uniformity. In order to promote
an uniform fermentation, a small portion of leaven
is intimately blended with a quantity of other
dough, which, by the aid of heat, diffuses itself,
and causes all the parts to ferment at the same
time. As soon as the dough has acquired a suffi-
cient bulk from the extrication of carbonic acid
gas, it is considered as fit for the oven. It will be
necessary here to consider more at large the nature
of the fermentation^ which is so essential in the
making of good bread.
When wheat-flour and water are mixed, the
saccharine extract of the flour, in consequence of
heat and moisture, has its constituent principles
disunited ; the oxygen seizes the carbon, forming
carbonic acid, which flies off in the form of gas,
and occasions that internal motion and increase
which appears. This process, if left to itself, is
extremely slow, and is therefore accelerated by the
addition of more dough and warm water. The
gluten, being dispersed through every part of the
mass, forms a membrane among the dougli, which
suffers the carbonic acid gas to expand, but pre-
vents its total escape, thus causing that porous
reticulated appearance, which fermented bread
MAKING BREAD. 15|
always has. As soon as the dough begins to sink
it is made up into the proper form, and put into the
oven, where tlie heat converting the water into an
elastic vapour, the loaf rises still more. The fer-
mentation by means of leaven is thought to be of
the acetous kind, because it is generally so managed
that the bread has a sour taste.
Bread made mth Yeast.
Yeast is the froth formed upon the surface of
beer, or ale, in a state of fermentation, and is com-
posed of carbonic acid gas inclosed in bubbles of
the mucilaginous liquor. When this is mixed with
dough, it causes it to ferment, and rise better and
more quickly than ordinary leaven ; and by this
means the best bread, and that now most generally
in use, is made.
Bread made with yeast is not only less compact,
lighter, and of a much more agreeable taste than
the preceding kinds ; but it is also more miscible
in water, with which it does not form a viscous
mass, a circumstance of the greatest importance
in digestion.
Bread, if well baked, is materially different from
flour and farinaceous cakes ; it no longer forms a
tenacious dough with water, nor can starch or
gluten be any more separated from it, : and hence
most probably its good qualities result.
The method of making common family bread is
as follows : to half a bushel of flour add six ounces
of salt, a pint of yeast, and six quarts of water that
has boiled ; in warm weather pour the water in
nearly cold, but it winter let it be lukewarm. Put
all these into a kneading-trough, and work them
together till they are the proper consistence of
dough. Cover up the dough warm that it may
L 4
152 MAKING BREAD.
ferment and rise. This is called setting the sponge.
After letting it lie the proper time, an hour and
a half, more or less, knead it well together, and
let it lie some time longer covered up. The oven
must in the mean time be heated : when this is
done, and it is properly cleaned, make the bread
into loaves, and place them in the oven to bake.
Household hread^ or brown bread, is baked in the
same manner, only of flour that is made from the
whole of the wheat, the bran as well as the flour
being ground together ; whereas in the white
bread, the coarser part of tlie bran is separated
from the flour. In what is called French bread,
the fermentation is carried on longer than in com-
mon bread, by which it becomes more porous, and
consequently lighter. Some bakers make a supe-
rior kind of French bread, by putting together a
peck and a half of the finest wheaten flour, called
Hertfordshire white, a pint of milk, a quarter of a
pound of salt, a pint and half of yeast, a quarter of
a pound of butter, two eggs, and three quarts of
water ; it is baked nearly in the same manner,
only frequently turning the bread in the oven.
The process used by the bakers for making
bread varies from what has been described, only
in circumstances depending on the great quan-
tity that is baked at a time. It is said that they
are apt to adulterate the bread sometimes with
alum, and also with chalk, and for this they are
severely punishable ; and any one suspecting it
may easily detect it by cutting a loaf in slices, and
mixing it with water which will dissolve the alum :
and it may then be obtained by evaporation.
Bread is made from the farinaceous grains ; but
of these, barley, oats, and rye, are most generally
used in Great Britain next to wheat. Wheat alone
MAKING BREAD, 153
possesses the gluten above described, which is so
useful in making the bread porous and light ; on
which account it is more difficult to make fer-
mented bread from the other grains : but this dif-
ficulty is obviated by adding to them a small quan-
tity of wheat flour, and many of them afford bread
nearly as nutritious, if not entirely so, as wheat.
It appears to be the fecula, or starch, that is the
the most nutritive part of the grain ; the potatoe,
which contains a great proportion of this substance,
forms the food of the most of peasantry in Ireland.
Ri/e h^ead is of a brownish colour, and has
rather a sweetish taste. It is much used in the
north of Europe, and also in some parts of this
kingdom ; but it is more usually mixed with a
quantity of wheaten flour.
Rye is also sometimes mixed with a fourth part
of ground rice, and makes a good and economical
household bread.
Bread has also been made by mixing turrdps and
flour in equal quantities. This requires rather
longer baking, and has at flrst a sweet taste, which
it loses on being kept twenty-four hours.
RicCy though usually prepared for food by boil-
ing, has been made into bread by mixing with it a
little flour, or potatoes.
Potatoes have also been made into bread by
mixing with them a quantity of wheaten flour,
BREWING.
The art of brewing, or of preparing a fermented
liquor called heer^ from farinaceous seeds, is very
ancient. It was known to the ancient Egyptians,
Spaniards, Germans, Gauls, inhabitants of the
British Isles, and of the north of Europe. The
l^l* BREWING.
liquor made by them, however, resembled more
our sweet and mucilaginous ales, the use of hops
being of modern invention.
Beer is made of an extract produced from malt
and hops by boiling ; and this extract is after-
wards fermented by adding yeast to it.
Malt is made from barley by a process which
is called malting. Barley is a grain consisting of
fecula, or starch, albumen, and a little gluten.
By the process of malting, its fecula is converted
into sugar, a substance essential to the production
of ardent spirit or alkohol, w^hich is the substance
that gives the intoxicating quality to every liquor.
To prepare malt, the grain is put into a trough
with water, to steep for about three days j it is
then laid in heaps, to let the water drain from it,
and afterwards turned over and laid in new heaps.
In this state, the same process takes place as if the
barley were sown in the ground; it begins to
germinate, puts forth a shoot, and the fecula of
the seed is converted into saccharine matter.
When this is sufficiently accomplished, which is
known by the length of the shoot, (about \ of the
length of the grain) this process of germination
must be stopped, otherwise the sugar would be
lost, nature intending it for the nourishment of
the young plant. The malt is, therefore, spread
out upon a floor, and frequently turned over,
which cools it, and dries up its moisture, without
which the germination cannot proceed. When it
is completely dried in this manner, it is called air-
dried malt, and is very little altered in colour.
But when it is dried in kilns, it acquires a brownish
colour, which is deeper in proportion to the heat
applied ; it is then called lUn-dried, This malt is
then coarsely gi'ound in a mill.
BREWING. 155
The quality of the beer depends upon the way in
which the malt has been prepared as well as the
quantity. There are three kinds of malt generally
used, pale, brown, and amber. Pale malt is dried
by a slow fire, and only so much as just to check
the future germination of the grain : it is dried
sometimes upon hair or wire sieves, which are made
to form the bottom of the kiln. Brown malt is
dried with a quick fire, and the outside is in fact a
little charred. Amber malt is intermediate be-
tween these two.
Pale malt is used for fine ales and pale beer :
brown malt is used for porter ; and amber is em-
ployed for brown ale and beer, and also to mix with
brown malt for porter, a practice which many prefer.
MasJiing is the next step in the process of brew-
ing. This is performed in a large circular wooden
vessel called the mash-tun, shallow in proportion
to its extent, and furnished with a false bottom,
pierced with small holes, and fixed a few inches
above the real bottom. There are two side open-
ings in the interval between the real and false
bottom : to one is fixed a pipe, for the purpose of
conveying water into the tun, and the other is for
drawing the liquor out of it. The malt is to be
strewed evenly over the false bottom of the same
tun, and then, by means of the side pipe, a proper
quantity of hot water is introduced from the upper
copper. The water rises upwards through the
malt, or, as it is called, the grist, and when the
whole quantity is introduced, the mashing begins,
the object of which is to efiect a perfect mixture of
the malt with the water, so that the soluble parts
may be extracted by it : for this purpose, the grist
is sometimes incorporated with the water by iron
rakes, and then the mass is beaten and agitated by
166 BREWING.
long flat wooden poles, resembling oars, which are
either worked by the hand or by machinery.
When the mashing is completed, the tun is co-
vered in, to prevent the escape of the heat, and the
whole is suffered to remain still, in order that the
insoluble parts may separate from the liquor : the
side pipe is then opened, and the clear wort al-
lowed to run off, slowly at first, but more rapidly as
it becomes fine, into the lower or boiling copper.
The chief thing to be attended to in mashing is
the temperature of the mash, which depends on
the heat of the water, and the state of the malt.
If the water was let in upon the grist boiling hot,
the starch which it contains would be dissolved,
and converted into a gelatinous substance, in
which all the other parts of the malt, and most of
the water, would be entangled beyond the possi-
bility of being recovered by any after-process.
The most eligible temperature appears to be
from 185° to 190^ Fahr. j for the first mashing, the
heat of the water must be somewhat below this
temperature, and lower in proportion to the dark
colour of the malt made use of. For pale malt
the water may be 180°, but for brown it ought
not to be more than 170°.
The liquor, or wort, as it is called, of the first
mashing, is always by much the richest in saccha-
rine matter ; but to exhaust the malt, a second
and third mashing is required, in which the water
may be safely raised to 190°, or upwards.
The proportion of wort to be obtained from
each bushel of malt depends entirely on the pro-
posed strength of the liquor. It is said that twenty-
five or thirty gallons of good table beer may be
taken from each bushel of malt. For ale and porter
of the superior kinds, only the produce of the
BREWING. 157
first mashing, or six or eight gallons, is to be em-
ployed.
Brewers make use of an instrument called a
sacchrometer, to ascertain the strength and good-
ness of the wort. This instrument is a kind of
hydrometer, and shows the specific gravity of the
wort, rather than the exact quantity of saccharine
matter which it contains.
The next process in brewing is boiling and
hopping. The hop plant is well known : hops con-
tain an aromatic and essential oil, having an agree-
able bitter flavour. Hops are necessary to prevent
the beer from passing into the acetic fermentation,
which would take place after the vinous ferment-
ation had ceased. They check the fermentation
in a great degree, so as to occasion it to go on
slowly, and thus to acquire strength ; and the quan-
tity of hops depends upon the length of time the
beer is intended to be kept. Hops are best when
new, as they lose much of their flavour by keeping.
If only one kind of liquor is made, the produce
of the three mashings is to be mixed together ; but,
if ale and table beer are required, the wort of
the first, or first and second mashings, is appropri-
ated to the ale, and the remainder is set aside for
the beer.
All the wort destined for the same liquor, after
it has run from the tun, is transferred to the large
lower copper, and mixed with a certain proportion
of hops. The better the wort, the more hops are
required. In private families a pound of hops is
generally used to every bushel of malt ; but in public
breweries, a much smaller proportion is deemed
sufficient. When ale and table beer are brewed
from the same malt, the usual practice is to put
the whole quantity of hops in the ale wort, which.
158 BREWING.
liaving been boiled some time, are to be transferred
to the beer- wort, and with it to be again boiled.
When the hops are mixed with the wort in the
copper, the liquor is made to boil, and the best
practice is to keep it boiling as fast as possible, till
upon taking a little of the liquor out, it is found to
be full of small flakes like that of curdled soap.
The boiling copper is, in common breweries, unco-
vered : but in many, on a large scale, it is fitted
with a steam-tight cover, from the centre of which
passes a pipe, that terminates by several branches
in the upper, or mashing copper. The steam,
therefore, produced by the boiling, instead of
being wasted, is let into the cold water, and thus
raises it very nearly to the temperature required
for mashing, besides impregnating it very sensibly
with the essential oil of the hops, in which the
flavour resides.
Vv^hen the liquor is boiled, it is discharged into a
number of coolers, or shallow tubs, in which it re-
mains until it becomes sufficiently cool to be sub-
mitted to fermentation. It is necessary that the
process of cooling should be carried on as expedi-
tiously as possible, particularly in hot weather ; and
for this reason, the coolers in the brewhouses are
very shallow. Liquor made from pale malt, and
which is intended for immediate drinking, need
not be cooled lower than 7-5 or 80 degrees ; of
course this kind of beer may be brewed in the
hottest weather ; but beer brewed from brown
malt, and intended to be kept, must be cooled to
65° or 70*^ before it is put into a state of ferment-
ation. Hence in the spring, the month of March,
and in autumn, the month of October, have been
deemed the most favourable for the manufacture of
the best malt liquor.
BREWING. 159
From the coolers the wort is put into the "work-
ing tun, in which it is mixed with yeast, in the
proportion of a gallon to four barrels of wort, in order
to excite the vinous fermentation. This process is
called tunning. By this the beer obtains its strength
and spirit ; the sugar extracted from the malt being
con\^erted into alkohol. In four or five hours the
fermentation begins. Its first appearance is by a
white line on the surface of the liquor, next to the
side of the vessel, which gradually advances to the
middle, till the w^hole surface is covered with a
scum, or froth, formed by innumerable minute
bubbles of carbonic acid gas, which rise through the
liquor. The temperature of the liquor increases,
and the whole is much agitated. The froth on the
surface accumulates, and constitutes the yeast. At
this time the presence of carbonic acid gas may be
easily perceived, by holding one's head over the
barrel or tun ; and fatal accidents have happened
through the accumulation of this gas in situations
where persons have been exposed to it without
being able to remove.
The vinous fermentation must be checked in
time, otherwise the acetous fermentation would
begin ; all the spirit would be lost, and the beer
would become sour.
The fermentation requires from 18 or 20 to 48
hours J and the beer is then put into smaller barrels,
called cleansing tuns. In them, the fermentation
goes on again, and during a fev/ days, a copious
discharge of yeast takes place from the bung-hole.
Care must be taken that the barrels are filled every
day with fresh liquor. This discharge gradually
becomes less, and in about a week it ceases j when
the bung-hole is closed.
The liquor is now suffered to stand for some
160 BLEACHING.
time tojine (or become transparent), by depositing
the mucilage that was suspended in it. When
there is time, the beer is allowed to fine itself; if
not, a preparation of isinglass and sour beer, called
Jinings, is put into it, to precipitate the mucilage.
A larger quantity of hops are used in porter than
for ales. Although in porter the brown malts are
necessary, it is bad economy to use them too highly
dried for the deepening of the colour, since the
consequence of drying too highly is a carbonization
of part of the saccharine matter. A dark colour
may be procured more economically by adding
burnt sugar to the wort.
It is in Britain prohibited by law to use any sub-
stance in brewing, as a substitute for hops.
BLEACHING.
Bleaching is the art of whitening cloths, made
from vegetable or animal substances, by depriving
them of their colouring matter. The art is of
great antiquity; and mankind, in all ages, appear
to have admired garments of a pure whiteness. The
effects produced by the air and rain upon vegetable
fibres exposed to them, must have led originally to
the idea of producing this by artificial means. The
ancients appear to have been acquainted with the
uses of soap and leys ; and to have practised bleach-
ing, nearly in the same manner as it existed among
us until lately. But few manufactures have received
so much benefit from modern chemistry, as that
now under consideration ; so that since the year
1786, it has undergone a complete change.
Bleaching ofLineth
The processes of bleaching difl'er materially,
according to the different materials of which cloths
BLEACHING. l6l
are composed: thus, linen, cotton, woollens, and
silk, are whitened by different methods. lu order
to understand the rationale of the bleaching pro-
cesses, it is necessary to be acquainted with the
nature of the materials.
Flax, from which linen is formed, is a vegetable
consisting of several coats or layers. The external
coat is a very thin bark ; under this is a green juice
or sap; next lies a layer of fibres or filaments,
which constitutes the part used for making linen ;
and, lastly, in the centre, there is a woody part. To
prepare flax for making cloth, the filaments or
fibrous part must be separated from the rest. The
filaments are held together by the sap, or succulent
part. To detach them from this, the flax is steeped
for several days in pools or ponds of soft stagnant
water; by which the putrefactive fermentation
takes place. But this fermentation must not be
suffered to proceed too far; otherwise the fibres
themselves would be aflR^cted by it, and their
texture injured. The flax must be taken out
while it is yet green, and while the wood breaks
easily between the fingers. The putrefaction of
the sap occasions the water in which the flax is
steeped to be extremely offensive ; and it is even
found that the fish are destroyed in any stream
where this process is used.
In some places, instead of steeping the flax in
water, it is simply exposed to the dew by laying it
on the grass.
The time required for this part of the process is
variable ; depending upon the state of ripeness of the
flax, the quahty and temperature of the water, and
other circumstances.
After steeping the flax, where the watering sys-
tem is practised, it is spread very thin on the grass,
VOL. II. M
l6^ BLEACHING.
and occasionally turned, until it is found to be very
brittlej so that on being rubbed between the
hands, the woody part easily separates. It is then
dried by the heat of the sun or of a kiln.
The flax is now ready to be beat or broke by a
mill for the purpose, or by mallets on a sort of
wooden anvil. The fibres of the flax are thus
separated from the wood, which is reduced to frag-
ments, most of which are cleared away by scutc7ii?ig.
To divide completely the fibres from each other,
and to separate the remaining part of the wood, the
process of hackling is employed. This consists in
drawing the flax through piles or groups of sharp
and polished iron spikes, placed close together, and
fixed in wood. The Ifackles are of various degrees
of fineness ; that is, the spikes are placed at different
degrees of distance from each other. The coarsest,
or most open hackles, are used first ; then a finer,
and so on, till the process is completed.
The flax is now ready to be spun into thread or
yarn, which is manufactured into cloth by the
weaver.
The linen, as it comes from the loom, is of a
brownish grey colour ; and it is then that the pro-
cess of bleachiuff- be^'ins.
The linen is first steeped in cold water for 48
hours, to discharge from it the weaver's dressing ;
which is a paste of flour and water, that had been
brushed into the yarn to enable them to stretch it
more easily.
The grey substance that colours the linen before
it is bleached is of a resinous nature, and conse-
quently it is insoluble in water. It is also intimately
united with the fibres of the flax, and is of difficult
separation. What appears to the eye to be a single
fibre is, in fact, a bundle of minute filaments, agglu-
^I,E ACHING. 163
dilated t.ogethei' by this resiijoijs matter. To sepa-
rate these filaments from eacli otlier, and to destroy
entirely the resinous colouring matter, is ^a process
of some difficulty. Solutions of alcalies rendered
caustic *5 called alcaline leySy have the property of
dissolving resins ; hence they have been used for
this purpose in bleaching. The linen is boiied in
water containing a quantity of ca'.:::;tic potash,
which acts upon the resiil of the external filaments,
and loosens them a little irom each Qther. The
cloth is then spread upon the grass, and exposed to
the action of the air, sun, and dew; and is also
occasionally watered. It is then returned again
into the bucking vat ; and the alkaline solution is
poured over it : by this another layer of the fila-
ments is opened, and the resin dissolved. It ds
then carried again to the field, and ti'eated as
before. In this manner, the ibucking and spreading
on the grass are repeated alternately, for 15 oi' 16
times, according to the weather and other circum-
stances, until the clotli is whitened. Were the
alcaline ley go strong as to dissolve xill the resin at
once, it would injure the texture of the fabric.
This alternate bucking and. exposing on the grass
is the old manner of bleaching, and was universally
used, till Scheele discovered the properties of the
oxygenated muriatic acid in destroying vegetable
colours. M. Bertholiet first applied this property
to the purposes of bleaching, and he, with great
liberality, communicated his observations to the
public. For this purpose, he immersed the cloth
into diluted oxygenated muriatic acid, between the
operations of the alcaline leys, which produced .the
* Common potash is rendered sufficiently.c^usdcfor the pur-
pose of bleaching, by adding to it quickhme, which nas a stronger
affinity for the carbonic acid than potash.
M S
I64f BLEACHING.
same effect in whitening it, as by exposing it to the
action of the air and light in the field.
The new method of bleaching was quickly and
successfully introduced into the manufactories of
France ; and almost as soon into those of Great
Britain. It is now universally adopted. The
advantages are, that the time required for bleach-
ing is shortened in a surprising degree so that
manufacturers experience a much quicker return of
their capitals ; and that it may be carried on at all
seasons of the year.
The first way in which the oxymuriatic acid was
applied in bleaching was in the liquid state ; that is,
when water is impregnated with the gas. The
goods were immersed in this liquid according to
the nature of the objects to be bleached. Skeins
of thread were suspended on frames in the tub in-
tended to receive them ; cloth was rolled upon
reels. When every thing was thus disposed, the
tubs were filled with oxygenated muriatic acid, by
introducing a funnel that descended to the bottom
of the tub in order to prevent the dispersion of the
gas. The cloth, or thread, was made to pass
through the liquid by turning the frames, until it
was judged that the acid was exhausted by acting
on the colouring matter.
But the volatility of this acid, and the suffocating
nature of its vapours, which produced extremely
noxious effects upon the health of the workmen,
rendered its use very difficult, although very in-
genious apparatus had been invented both by Ber-
thollet and by Mr. Watts. It was also found diffi-
cult to cause the acid to act upon all parts of the
cloths equally, when they were stratified in the cis-
terns with the acid.
A considerable improvement was made in the
BLEACHING. 16.5
apparatus by Mr. Rupp of Manchester, which is
described in the Manchester Memoirs. Still it
was found that the acid alone was apt to weaken
the cloth, and that it injured the health of the
workmen.
At length it was discovered by some manufac-
turers at Javelle, near Paris, that the addition of
an alkali to the liquor deprived it of its suffocating
effects, without destroying its bleaching powers.
Potash was the alcali they employed ; and this so-
lution was called the Javelle liquor. The invent-
ors came into this country, and established a
bleaching-work. The process was then carried on
in open vessels ; and the bleacher was able to work
his pieces in the liquid, and expose every part to
its action without inconvenience.
Although these advantages were unquestionably
great, they were diminished by the heavy expense
of the alcali, which was entirely lost. Also, the
the potash, which added to the liquor, though it did
not destroy its power of bleaching, diminished it;
because a solution of the oxygenated muriate of
potash, which differs from this bleaching-liquor in
nothing but in the° proportion of alcali, will not
bleach at all. This is a well-known fact; from
which we might infer, that the oxygenated muri-
atic acid will lose its power of destroying the co-
louring-matter of vegetable substances, in propor-
tion as it becomes neutralized.
Mr. Tennant discovered that lime might be
substituted for the potash, the oxymuriatic acid
combining with all the alcaline earths, and forming
oxymuriates which were soluble in water, and had
the property of bleaching. This is the substance
nov/ employed. If the oxygenated muriatic acid
be passed through lime-water, it will combine with
M 3
1©6 BLEACHING.
the lime, and form oxymuriate of lime ; but as the
water can only retain a small portion of lime, this
was not found of much use. To cause a larger
quantity of lime to combine with the oxymuriatic
acid gas, the lime is mechanically suspended by
agitation in the water into which the gas is made
to passj so as to present fresh matter to the gas.
By this means, the oxymuriatic acid combines with
the lime, forming a compound soluble in the
water : this is used as a bleaching-liquor.
The oxygenated muriatic acid gas may also be
combined with lime in a dry state. To effect this,
the oxymuriatic acid gas is sent into a vessel contain-
ing dry hydrate of lime (that is, lime slacked with
water) : the powder is agitatedj and the gas com-
bines with it to a certain amount, or till the hy-
drate of hme becomes saturated. The compound
is a soft white powder, possessing little smell. It
is partially soluble in water, yielding a solution
much the same as that obtained by the former
process.
Although most salts that are soluble in Water
are capable of being formed again by evaporating
the water, either in crystals or in a dry Saline mass,
this is not the case with oxymuriate of lime. When-
ever a solution of it is evaporated, part of the acid
escapes, and the rest is mostly converted into mii-
riatic acid ; so that ins,te?A of oa^i/jrmriate of lime,
muriate of lime is obtained. Hence the dry salt
cannot be obtained from the liquid solution.
The dry oxymuriate of lime may be very Con-
veniently transported without injury, an advantage
not possessed by the acid alone, which cannot be
transported without the loss of almost half its
strength : but it must be observed that the dry
salt is much imjiaired by being long kept.
BLEACHING. l67
*'We have hitherto used the old term of oxynuiri-
atic acid, because it is best known by this name in
the bleaching processes ; but it will be remem-
bered that this substance is now considered as a
simple body, and is known by the name of chlorine.
What has just been called oxymuriate of lime
is known among modern cliemists by the term
cldorate of lime.
The oxymuriatic acid gas, or chlorine, may be
procured by distilling muriatic acid in black oxide
of manganese ; but to save the expense of first
preparing the muriatic acid, the usual practice in
bleaching is to mix three parts of black oxide of
manganese with eight parts of muriate of soda or
common salt, and five parts sulphuric acid, diluted
with four parts water.
To ascertain the strength of the liquid for
bleaching, a solution of indigo in the sulphuric acid
is employed. The colour of this is destroyed by
the oxygenated muriatic acid; and according to the
quantity of it that can be discoloured by a given
quantity of the liquor, its strength is known.
The linen is usually not immersed in the solution
of oxymuriate of lime until after the fourth or fifth
bucking ; because a great portion of the resin is
removed cheaper by the alkaline leys, and washing
in water.
Tlie last operation in bleaching is souring, or
steeping the linen in some sour liquid of a blood
heat. For this purpose, formerly sour milk was em-
ployed : but now sulphuric acid is used. Of this
as much is put into water as will give it the acidity
of vinegar. The linens are generally steeped about
twelve hours, and are tlien well washed. This
souring is essential to the procuring of a good white,
but the theory of its action is not well understood.
TNI 4
168 BLEACHING.
Nothing now remains, in order to complete
them for the market, but rubbing them with a
strong lather of soap, washing, and blueing them.
The alcali is one of the chief articles of expense
used in bleaching : and it is a great object with
the bleacher to recover the pure alcali from the
leys which have been used.
The sulphuret of lime, or the combination of
sulphur and lime, which are both cheap articles,
has been used in Ireland for bleaching, instead of
potash. It was first proposed by Mr. Higgins, and
it answers in some cases, particularly where the
goods are intended for dying.
The sulphiu'et of Hme is prepared as follows: —
sulpliur in powder, four pounds j lime, well slaked,
twenty pounds ; and water, sixteen gallons ; are
to be well mixed, and boiled for half an hour in an
iron vessel, stirring them briskly from tim.e to time.
Soon after the agitation of boiUng is over, the so-
lution of the sulphuret clears, and may be drawn
off free from the insohible matter, which is consider-
able, and whicli rests upon the bottom of the boiler.
The liquor in this state is pretty nearly of the
colour of small beer, but not quite so transparent.
Sixteen gallons of fresh water are afterwards to
be poured upon the insoluble dregs in the boiler,
in order to separate the whole of the sulphuret
from them. When this clears (being previously
well agitated) it is also to be drawn off and mixed
with the first liquor ; to these again, thirty-three
gallons more of water may be added, which will
reduce the liquor to a proper standard for steeping
the cloth. Here we have (an allowance being
made for evaporation, and for the quantity re-
tained ill the dregs) sixty gallons of liquor from
four pounds of sulphur.
BLEACHING. IgQ
Althougli sulphur, by itself, is not in any sensible
degree soluble in water, and lime but sparingly so,
water dissolving only about one seven hundredth
part of its weight of lime ; yet the sulphuret of
lime 19 highly soluble.
After the paste used by the weaver has been re-
moved, the linen is steeped in a solution of the
sulphuret of lime, prepared as above, for about
twelve or eighteen hours. It is then washed, and
steeped in oxymuriate of lime. This process is
repeated by six alternate immersions in each liquor.
For the use of private families, where the linen is
dirtied by perspiration or grease, it will be of great
service towards rendering it white, to steep it for
some time in a clear liquor, made by mixing one
quart ofquick-Ume in ten gallons of water, letting
the mixture stand for twenty-four hours, and then
using the clean water drawn off from the lime.
After the linen has been steeped in this liquor, it
should be well washed as usual, but will require
much less soap to be used.
It is of great consequence in bleaching with the
oxygenated muriatic acid, that it may be employed
of a proper strength ; as a test to ascertain its
strength, a solution of indigo in sulphuric acid is
used. A certain quantity is put into a glass tube,
and Oxygenated muriatic acid is added until the
colour of the indigo is destroyed : by the quantity
of acid necessary to destroy the colour, its strength
is estimated.
Steam has been employed in bleaching in France
with great success. The process was brought from
the Levant. Chaptal lirst made it known to the
public. When an aicaline ley is boiled, a certain
quau-tity of aicali always rises with ihe steam. The
170 BLEACHING.
cloth is first immersed in weak caustic alcaline
liquor, and placed over a chamber constructed over
a boiler, into which is put the alcaline ley which is
to be raised into steam. After the fire has been
lighted, and the cloth lias remained exposed to the
action of the steam for a sufiicient length of time,
it is taken out, and immersed in the oxygenated
muriate of lime, and afterwards exposed for two
or three days on the grass.
This operation, which is very expeditious, is suf-
ficient for cotton ; but if linen-cloth should still
retain a yellow tint, a second alcaline vapour-bath,
and two or three days exposure on the grass, will
be sufficient to give them the necessary degree of
whiteness.
Bleaching of Cotton.
Cotton is a vegetable substance, and the pro-
duction of a shrub that grows only in warm climates.
It is a fine downy substance, in which the seeds of
the plant are inclosed. Cotton, in its natural state,
is generally of a dirty yellow, and opaque, being-
covered with a colouring matter of an unctuous
nature ; when this is removed, it is white and
transparent.
Cotton is easier to bleach than linen. The
colouring-matter is dissolved by the action of alca-
line leys and washing. Sometimes the oxymuri-
atic acid is also used to expedite the process.
Steeping in diluted sulphuric acid, is also used to
dissolve the earthy matter that always remains after
the immersion in alcaline ley; and as cotton is not
so easily injured by acids as flax, more use is made
of the acid than in the bleaching of linen. The
BLEACHING. I7I
action of steam is very efficacious in bleaching
cottons.
In bleaching cotton for calico-printing, a pure
white is not so much sought for, as that the oil
may be entirely extracted.
In applying the alcaline ley, great care must be
taken that no lime remains in suspension in the
liquor, as it might be fixed in the cloths ; and when
the sulphuric acid is used, a sulphate of lime would
be formed, which in fact is a mordant for the
madder ; hence the latter could not be discharged
from those parts intended to be white.
For the same reason, the oxy muriate of lime can-
not be used, if madder is to be discharged from
any part of the cloth. When this is the case, oxy-
muriate of potash, or of soda, is substituted for
oxymuriate of lime.
Bleaching of Wool.
The bleaching of animal substances is somewhat
different from the processes employed for vegetable
substances.
Wool is a sort of very fine hair which covers the
bodies of some animals. Each hair is hollow, and
contains an oily matter.
Wool is not easily acted upon by acids ; is unalter-
able by water, cold or boiling; but may be entirely
dissolved by strong alcaline leys. On this account,
the latter must be used with great caution.
Wool is oiled before it is combed and spun, and
the first operation is to free it from the oil which
it has thus acquired. This is called scouring. Stale
urine, which contains ammonia or the volatile
^Icali, is mixed with water ; and the wool is im-
17^ BLEACHING.
mersed in this for about twenty minutes, heated to
56° Fahr. It is then taken oat, drained, and
rinsed in running water ; then put into the bath of
urine, and washed again. This is sometimes re-
peated a third time, and sometimes scouring with
soap is used.
Fulling the cloth adds also to its whiteness.
Fulling is a species of scouring with a particular
kind of earth called J}dler's earth. It effectually
removes all grease, from the chemical affinity
existing between the alumina contained in the
fuller's earth and the oil of the cloth ; and thus dis-
poses the fibres to be entangled and matted toge-
tiier in the subsequent process of milling, employed
to thicken the cloth, and render it stronger and
firmer.
Scouring entirely with soap is preferred when
the articles are valuable.
Sulphureous acid is also used for giving the last
degree of whiteness.
Sulphuring is performed in the following man-
ner. The articles to be whitened are suspended
iiopn poles across a chamber, constructed so as
to be perfectly close. Into this chamber is pre-
viously put a quantity of sulphur in dishes. When
the cloth is in, the sulphur is set fire to, and the
doors of t]ie chamber are accurately sliut, and all
the interstices carefully stopt up, so as to exclude
entirely the atmospheric air.
The combustion of the sulphur produces a va-
pour which is the sulphureous acidj this destroys
the colouring matter of the wool, whicli is conse-
quently rendered white. The time necessary for
this process varies from six to twenty-four hours.
The cloth is left in the clianiber for some time
after the combustion of the sulphur has ceased 4 it
BLEACHING. 173
is then taken out and rinsed, to remove the acid;
and afterwards washed with soap, to give a degree
of softness.
This mode of bleaching by the combustion of
sulphur is also used for other substances, as straw
in the manufacture of hats, &c.
A superior method of employing the sulphureous
acid in bleaching is the following. Water is im-
pregnated with the sulphureous acid, and tubs are
filled with this; then the stuffs are drawn through
it upon reels, till they are whitened. The sulphur-
eous iicid is made by decomposing the sulphuric
acid by the addition of any combustible matter
capable of taking away a part of its oxygen. A
cheap method of effecting this is by putting chopped
straw, or saw-dust, into a nlattrass, and then pour-
ing over it sulphuric acid, and afterwards applying
heat. The sulphureous acid gas will be formed,
but will be combined with the water in the vessel.
The stuffs are then taken out, and left to drain
upon a bench covered with cloth; a precaution
which is necessary, because the wood might be
decomposed by the sulphuric acid, and would stain
the goods. They are afterwards washed in clear
water. It is generally necessary to sulphur them
twice before the white is sufficiently bright. Some-
times Spanish white is put into the water used for
washing them; and they are also aziired or blued
bv disolvino^ some Prussian blue in the water.
Nothing then remains to be done but dryings
stretching J and pressing.
Bleaching of Silk.
Silk is an animal substance, and is prepared by
a caterpillar, usually called the silk-worm. This
174^ BLEACHING.
insect inhabits warm climates, and cannot be reared
in this country without difficulty, nor in sufficient
quantity for the purpose of procuring silk. The
south of Europe and Asia are its proper countries.
The silk is spun by the silk-worm in the form of
threads of a semi-transparent matter, which it winds
up round itself when it passes into the crysalis
state. The threads, when formed, are connected
together by a viscous substance, from which they
must be separated before they can be wound off,
by putting them into hot water.
The silk itself is covered with a yellow varnish,
which is soluble in alcaline leys ; and as this varnish
conceals the lustre of the silk, it is necessary to
detach it. Silk is itself soluble in strong alkaline
leys ;| care must be taken, therefore, not to injure
the silk in taking off the varnish. Water at a boil-
ing heat has no action on silk ; but steam dissolves
its varnish.
In France they proceed as follows. They fill a
boiler with a very weak solution of caustic soda,
and place in a chamber connected with tlie boiler,
the skeins of raw silk, wound on frames ; then they
close the door of the chamber, and make the solu-
tion in the boiler boil. Having continued the
ebullition for twelve hours, they slacken the fire,
and open the door of the chamber. The steam,
which is always above 250° Fahr., will have dis-
solved the gum of the silk. The skeins are then
washed in warm water, wrung, and boiled a second
time ', then washed again several times with soap,
till they have acquired the necessary whiteness and
softness.
It is not possible, however, to give to silk all the
necessary splendour by this process alone ; to com-
plete it, the silk must be exposed to the action of
the sulphureous acid, either in the form of gas, or
combined with water, as directed for wool.
Bleaching Prints and Frinted Books.
An application has been made of the new mode
o^ bleaching to the whitening of books and prints
that have been soiled by smoke and time.
Simple immersion in oxygenated muriatic acid,
letting the article remain in it a longer or shorter
space of time, according to the strength of the li-
quid W'ill be sufficient to whiten an engraving.
If it be required to whiten the paper of a bound
book, as it is necessary that all the leaves should
be moistened by the acid, care must be taken to
open the book well, and to make the boards rest
upon the edge of the vessel in such a manner that
the paper alone be dipped in the liquid : the leaves
must be separated from each other, so that they
may be equally moistened on both sides.
The liquor assumes a yellow tint, and the pa-
per, becomes white in the same proportion j at the
end of two or three hours the book may be taken
from the acid liquor and plunged into pure water,
with the same care and precaution as recommended
in regard to the acid liquor, that the water may
exactly touch the two surfaces of each leaf. The
water must be renewed every hour, to extract the
acid remaining in the paper, and to dissipate the
disagreeable smell.
By following this process, there is some danger
that the pages will not be all equally whitened,
either because the leaves have not been sufficiently
separated, or because the liquid has had more ac-
tion on the front margins than on those near the
176 BLEACHING.
binding. On this account, the best way is to de-
stroy the binding entirely, that each leaf may
receive an equal and perfect immersion ; and this
is the second process recommended by M.
Chaptal.
" They begin," says he, " by unsewing the book,
and separating it into leaves, which they place in
cases formed in a leaden tub, with very thin slips
of wood or glass ; so that the leaves, when laid flat,
are separated from each other by intervals scarcely
sensible. The acid is then poured in, making it
fall on the sides of the tub, in order that the leaves
may not be deranged by its motion. When the
workmaa judges, by the whiteness of the paper,
that is has been sufficiently acted upon by the
acid, it is drawn off by a cock at the bottom of the
tub; and its place is supplied by clear fresh water,
w^hich weakens and carries off the remains of the
acid, as well as the strong smell. The leaves
are then to be dried, and, after being pressed, may
be again bound up.
" The leaves may be placed also vertically in the
tub ; and this position seems to possess some ad-
vantage, as they will be less liable to be torn.
" With this view, I constructed a wooden frame,
which I adjusted to the proper height, according
to the size of the leaves I wished to whiten.
" This frame supported very thin slips of wood,
leaving only the space of half a line between them.
I placed two leaves in each of these intervals, and
kept them fixed in their place by two small wooden
wedges which I pushed in between the slips.
" When the paper was whitened, I lifted up the
frame with leaves, and plunged them in cold water,
to remove the remains of the acid as well as the
smell ; this process I prefer to the other.
BLEACHING. 177
" By this operation, books are not only cleaned,
but the paper acquires a degree of whiteness su-
perior to what is possessed when first made.
" The use of this acid is attended also with the
valuable advantage of destroying ink-spots. This
liquor has no action upon spots of oil or animal
grease ; but it has been long known that a weak
solution of potash will effectually remove stains of
that kind,
" When I had to repair prints so torn that they
exhibited only scraps pasted upon other paper, I was
afraid of losing these fragments in the liquid, be-
cause the paste became dissolved. In such cases,
I enclosed the prints in a cylindric glass vessel,
which I inverted on the water in which I had put
the mixture proper for extricating the oxygenated
muriatic acid gas. This vapour, by filling the
whole inside of the jar, acted upon the print, ex-
tracted the grease as well as ink-spots, and the
fragments remained pasted to the paper."
Bleaching of Paper.
The oxygenated muriatic acid has also been ap-
plied to the bleaching of paper, which it has ren-
dered considerably more expeditious.
Bleaching of old printed papers to he xvorked up
again. — Boil the paper for an instant in a solution
of soda, rendered caustic by potash. Steep it in
soap water, and then wash it, after which tlie pa-
per may be reduced to a pulp by the paper-mill.
Bleaching of old written papers to he worked
again. — Steep the papers in a cold solution of sul-
phuric acid in water, after which wash them before
they are taken to the mill. If the acidulated wa-
ter be heated, it will be the more effectual.
VOL. II. N
17^ DYEING,
Bleaching of printed papers "without destroying
the texture qf^ the leaves. — Steep the leaves in a
caustic solution of soda, and afterwards in one of
soap. Arrange the sheets alternately between
cloths in the same manner as paper-makers dispose
their sheets of paper when delivered from the
form. Put the leaves in a press, and they will be-
come whiter, unless they were originally loaded
with printers' ink or size. If this should not com-
pletely effect the whitening of the leaves, repeat,
the process a second, or even a third time.
Bleaching coloured rags to make ichite paper. —
Soak or macerate the rags sufficiently ; put them
into a solution of caustic alcali, and then into the
oxygenated muriatic acid ; and, lastly, steep them
into diluted sulphuric acid.
DYEING.
Dyeing is the art of extracting the colouring
principle from different substances, and transfer-
ring them to wool, silk, cotton, or linen. AVlien
other matters are coloured, the process is called
staifiing.
In dyeing, the colouring matter is not merely de-
posited on the stuff, but is firmly attached to it by
chemical combination depending on an affinity
subsisting between them.
If the colouring matters were merely spread
over the surface of the fibres of the cloth, the co-
lours produced might be very bright, but they
would not be permanent, since they would be
rubbed off, and would disappear when the cloth Vvas
washed, or even by exposure to the weather. Dye-
ing is, therefore, a chemical process, consisting in
combining a certain colouring matter with fibres of
cloth, 'the colouring matters are, for the most
part, extracted from animal and vegetable sub-
stances, and have usually the colour which they
give to the cloth.
The particles of these colouring matters appear
to be transparent, because the original colour of
the cloth will appear through them. The colour
of dyed cloth, therefore, does not depend upon the
dye alone, but also upon the previous colour of the
cloth. Thus, if the cloth be black it will not re-
ceive a dye of any colour ; and hence it is neces-
sary, that the cloth should be white, if we wish to
dye it of a very bright colour.
The colouring matter, or dye-stuff, must be dis-
solved in some liquid, that the particles may be
precipitated upon the cloth ; and it is essential
that its affinity for this solvent should not be so
strong as for the cloth to be dyed.
Thus the facility with which cloth imbibes a dye
depends upon two things ; namely, the affinity be-
tween the cloth and the dye stuff, and that between
the dye stuff and its solvent. Much of the accu-
racy of dyeing depends upon preserving a due
proportion between these two affinities. If the
affinity between the dye-stuff and cloth, compared
with that between the dye-stuff and the solvent be
too great, the cloth will receive the dye tOb quickly,
and the colour will be apt to be Unequal : and if
the affinity between the dye-stuff and the solvent be
greater than between the dye-stuff and the cloth,
the latter will scarcely receive the dye, br, at least,
very faintly.
JVool has the strongest affinity for colouring-
matters ; silk the next strongest ; cotton lias much
less affinity ; and linen has the least of all. Hence
the dye-stuff for cotton or linen shotild be dissolvetl
N 9
180 DYEING.
ill substances which they have less affinity for, than
when silk or wool are to be dyed. Thus iron dis-
solved in the sulphuric acid may dye wool ; but
when it is intended to dye cotton and linen by
iron, the latter should be dissolved in the acetous
acid.
There are few colouring substances that have,
of themselves, so strong an affinity for cloth as to
answer the purpose of dyeing so as to remain per-
manent ; and, on this account, an intermediate
substance is employed, that has a decided attraction
for both the colouring matter and the cloth, thus
serving as a bond of union between them. This
substance is previously combined with the cloth,
which is then dipped into the solution containing
the dye-stuff. The dye-stuff combines with the in-
termediate substance, which being firmly combined
with the cloth, secures the permanence of the dye.
Substances employed for this purpose are deno-
minated mordants. Instead of this some prefer the
term basis.
The most important part of dyeing consists in
the proper choice, and the proper application of
mordants; as upon them, the permanency of every
dye depends. What has been said respecting the
application of colouring matters applies equally to
the application of mordants. They must be pre-
viously dissolved in some liquid, which has a
weaker affinity to them than the cloth has, to
which they are to be applied ; and the cloth must
be dipped, or even steeped in this solution, in
order to saturate itself with the mordant. The
mordants are earths, metallic oxides, tan, and oil.
Of the earths, alumine is the most useful. It is
applied in the state of sulphate of alumine, or
common alum j and in that of acetate of alumine.
DYEING. 181
When alum is used as a mordant, it is dissolved
in water, and sometimes a quantity of tartar is
added. The cloth is put into this solution, and
kept till it has absorbed as much alumine as is ne-
cessary. It is then taken out, and is washed and
dried. A quantity of alumine has by this process
combined with the fibres of the cloth, which is
perceived by the latter weighing more than before.
The addition of the tartar, or tartrate of potash, is
made on two accounts ; the potash which it contains
combines with the sulphuric acid of the alum, and
thus prevents that very corrosive substance from
injuring the texture of the cloth : the tartareous
acid, on the other hand, combines with part of the
alumine, and forms a tartrate of alumine, which is
more easily decomposed by the cloth than alum.
Acetate of alumine is used as a mordant for
cotton and linen, which have a much less affinity
than wool for alumine. The alumine is retained less
powerfully in a state of combination by the acetic
than by the sulphuric acid ; and, therefore, cotton
and linen are better able to separate it and attach
it : also the acetic acid being volatile, gradually
leaves the earthy basis, and allows the alumine to
unite to the stuff*.
This mordant is now prepared by pouring acetate
of lead into a solution of alum j on which a double
decomposition takes place ; the sulphuric acid com-
bines with the lead, and the sulphate of lead pre-
cipitates in the form of an insoluble powder, while
the alumine combines with acetous acid, and
remains in the liquor.
This mordant gives a richer colour than alum.
Liine is also sometimes employed as a mordant :
but it does not answer so well in general, not giving
so good a colour. It is used either in the state
N 3
of limip v/at;er, or as sulphate of lime dissolved in
water.
Although all the metallic oxides have an affinity
for cloth, only two, the oxides of tin and of iron,
are much used as mordants.
The oxide of tin is one of the most valuable mor-
dants, and is the only one by which scarlet, the
brightest of all colours, can be produced. It was
first brought to London by Karsten, a German, in
1543, which period forms an epoch in the history
of dyeing.
Prous^ 1]^S shown that tin has two oxides. The
first, pr grey oxide, consists of seventy parts of tin,
ai:id thirty oxygen : the second, or w^hite oxide, of
sixty parts of tin, and forty oxygen. The first ox-
ide absorbs oxygen rapidly from the air, andbecomes
converted into the white oxide. It is, therefore,
the white oxide alone that is the real mordant ;
since if the first were applied to cloth, as it proba-
bly often is, it must soon be converted info the
white pxide by absorbing oxygen.
Tin is used as a mordant in three states ; dis-
solved in nitro-muriatic acid, in acetous acid, and
in a mixture of sulphuric and muriatic acids.
That commonly used by the dyers, ^nd called by
them sphit of tin, is the nitro-muriate. It is pre-
pared by dissolving granulated tin in very dilute
nitric acid, or what is called single aquafortis : and
a quantity of muriate of soda, or muriate of am-
monia, is added. These salts are decomposed by
the nitric acid, and the muriatic acid is set free,
sometimes to economize the nitric acid, a quan-
tity of sulphuric acid is added, just sufficient to
saturate the base of the muriate of soda.
When nitro-muriate of tin is used as a mordant,
it is dissolved in a large quantity of water, and
tartar is added. The cloth is then put in and kept
till it is saturated. A double decomposition takes
place ; the nitro-muriatic acid combines with the
potash of the tartar, Avhile tlie tartareous acid dis-
solves the oxide of tin. When tartar is used,
therefore, in any considerable quantity, the mor-
dant is not a nitro-muriate, but a tartrate of tin.
The mur'iu-sidphate of tin, produced by dissolving
tin in muriatic acid, combined with about one-
fourth of its weight of oil of vitriol, is also a valuable
mordant, and is preferable to the last for some pur-
poses J it is also less expensive.
The oxide of iron is also a very useful mordant,
and all kinds of cloth have a strong affinity for it.
The permanency of the iron spots on linen and
cotton is a sufficient proof of this. Iron, as a mor-
dant, is used in different states. Wool is dyed
generally by means of the sulphate of iron, which
may also be used for cotton. Acetate of iron, pre-
pared by dissolving iron in vinegar, sour beer, Sec,
is preferable for some purposes. The pyro-lig-
neous acid, which differs from the acetic only in
having in combination a certain quantity of empy-
reumatic oil, is at present preferred to the sulphuric,
or acetic.
The astringent principle, or tannin, is also em-
ployed as a mordant, and has a strong affinity for
cloth, and also for colouring matters. An infusion
of nut-galls, sumach, oak bark, or any other sub-
stance containing tannin, is made in water, and the
cloth is kept in it till it has absorbed a sufficient
quantity oi tannin. Silk has so strong an affinity
for tannin, that manufacturers sometimes employ
this circumstance to increase the weight of their silk.
A compound mordant is sometimes produced by
impregnating the cloth first with oil, then with the
N 4"
184 DYEING.
astringent principle, and, lastly, with the aluminous
mordant. This is employed in dyeing the Adria-
nople red.
Several other substances are used as mordants
occasionally, either as principals, or to facilitate the
combinations of others with the cloths ; such as ni-
trate of bismuth, oxide of arsenic, corrosive sub-
limate, acetate of lead, sulphate, or acetate of
copper, &c.
The chief use of mordants is to render the dyes
permanent, but they have also considerable in-
fluence on the colour produced : thus, the same
colouring matter will produce very different dyes,
according to the mordant used to fix it. If the
aluminous mordant be used for cochineal, the colour
will be crimson ; but if the oxide of iron be used for
the same colouring matter, black will be the result.
It is necessary, therefore, to choose such mor-
dants and colouring matters as together shall pro-
duce the desired colour. And this principle
enables us also to produce various colours with
the same dye-stuff, only by changing the mordant.
It is probable that the whole of the surface of
the fibres of cloth are not covered by the colouring
matters precipitated upon them ; but that the
particles of colour are at some distance from each
other. For cloth may be dyed different shades of
the same colour; that is, it may be dyed deeper a
second time than at first, by increasing the quan-
tity of colouring matter, which could not be tlie
case if the whole surface were covered. Another
circumstance renders this opinion probable ; all
those colours which dyers call compound are made
by dyeing the cloth first one colour, and then
another : thus, green is got by dyeing cloth first
blue and then vellow.
DYEING. 185
In dyeing, the water employed should be as
pure as possible, and the exact temperature in each
process should be attended to. The dye-houses
should be spacious, light, and airy, and cleanness is
essentially necessary. The stuffs are supported in
the cauldrons, or baths, by proper apparatus, and
are drawn through them by a winch, or reel.
Of Dyeing Red,
The colouring matters employed for dyeing red
are cochineal, kermes, madder, lac. Brazil-wood,
logwood, and earth amus. Cochineal is a species
of insect (the coccus cactiy Lin.) brought from
America. The decoction of it affords a very bright
crimson colour, inclining to violet. When alum
is added to this decoction, it combines wdth its
colouring matter, and forms a red precipitate.
Muriate of tin gives a still more beautiful colour.
Kermes is also an insect found in several parts
of Asia, and the south of Europe, which furnishes
a red dye, by some thought not inferior to cochi-
neal, but which has not been so much used since
the introduction of the latter.
Madder is the root of a plant (rubia tinctoriuniy
Lin.) The colouring matter of madder is extracted
by water, either cold or hot, and precipitates of
various shades of red may be obtained by alum,
chalk, acetate of lead, and muriate of tin.
Lac is a colouring matter of animal origin, pro-
duced in the East Indies, from tlie coccus lacca^ a
small winged insect. This insect forms cells for
its young, as regular as the honey-comb, but diffe-
rently arranged ; and the lac is procured from the
substance of which these cells are made. The whole
matter of these cells is called stick lac ; when the
1 86 DYEING
"s >-
^?^
red colouring matter is extracted by water, what
remains is a resinous substance called shell lac^ used
for various purposes, as varnishes, sealing wax, &c.
Water dissolves lac, and the decoction is of a deep
crimson colour. The precipitate, with alum or
nitro-muriate of tin, forms a fine red.
Brazil-wood is an article used in dyeing. It is
the central part of a large tree, that grows in Brazil.
It is heavier than water, and affords a decoction of a
red colour with water. The precipitate, with alum
and nitro-muriate of tin, is a fine red.
Peach-wood gives a colour inferior to Brazil, and
also in smaller quantity.
Logwood affords a colouring matter extensively
used in dyeing. It is very heavy, and sinks in
water. Its decoction is yellow, but by alum be-
comes violet or purple ; by sulphate of iron it
becomes black.
Carthamus is the flower of a plant cultivated in
Spain and the Levant. It contains two colouring
matters ; a yellow, which is soluble in water ; and
a red, which is insoluble in water, but soluble in
alcaline carbon ats. The red colouring matter of
carthamus, extracted by carbonate of soda, preci-
pitated by lemon-juice, and ground with talc, con-
stitutes the rouge employed as a cosmetic: the
fineness of the talc, and the proportion of it mixed
with the carthamus, occasion the difference between
the cheaper and dearer kinds of rouge.
Wool is died scarlet, which is the most splendid
of all reds, by cochineal. Alum will do as a mor-
dant for fixing the red ; but nitro-muriate of tin,
or what is still better, the murio-sulphate of tin, are
now used as preferable mordants. To die wool
scarlet, a bath is made by mixing pure tartar with
a little cochineal and nitro-muriate of tin 5 but as
DYEINGf. 1P7
the red prodiiced by cochineal alone is rather a
crimson than a scarlet; and as the colour of scarlet
is, in flict, crimson and yellow, some yellow dye,
or fustic, turmeric, or quercitron bark, is added to
the cochineal in the first bath.
Into this the cloth is put, and boiled for two
hours. It is then waslied, and afterwards put into
a second bath of cochineal, which is called the red-
dening. When crimson is the colour to be given
to the cloth, the tin mordant is the best; but some-
times the dyers use the alum for this purpose, and
then a decoction of cochineal. The addition of
archil and potash renders the crimson darker, and
gives it more bloom, but this is very fugitive. For
paler crimsons, some madder is substituted for a
portion of the cochineal. Wool is dyed madder-red,
by boiling it first two or three hours with alum and
tartar, and then in a bath of madder.
Silk may be dyed crimson with cochineal or
Brazil-wood, and sometimes carthamus is used. The
nitro-muriate of tin is the best mordant, but alum
may be also used. Madder does not give a colour
sufficiently bright.
Poppy colour, cherry, rose, and flesh colour, are
given to silk by carthamus or Brazil-wood. When
the carthamus is employed, an alcaline solution is
made, and as much lemon-juice as will give it a
fine cherry-red is poured into it.
It is extremely difficult to give silk a scarlet, and
it is scarcely possible to give it a full scarlet. The
murio-sulphate of tin, as a mordant, is first used,
then the bath of cochineal and quercitron, and
lastly, the cochineal bath alone. A colour approach-
ing to scarlet may also be given to silk, by dyeing-
it first crimson, then dyeing it with carthamus, and
lastly yellow, without heat.
188 DYEING.
Cotton and linen are dyed red with madder.
Cochineal, which gives so fine a red to wool, by the
nitro-muriate of tin, communicates only a dirty red
to cotton and linen, by the same means.
Madder reds are of two kinds. 1. The common
madder red, which is formed by impregnating the
cotton or linen with galls, and afterwards alumed,
and then putting them into the madder bath.
2. The Adrianople, or Turkey red. This process
was brought from the East. It is more durable
and more beautiful than the common red. The
cloth is first impregnated with oil, then with galls,
and lastly, with alum. It is then boiled for an
hour, in a decoction of madder, which is commonly
mixed with a quantity of blood. After the cloth is
dyed, it is plunged into a soda ley, in order to
brighten the colour. The chief difficulty is in
the application of the mordant, which is the
most complicated employed in the whole art of
dyeing.
Cotton may be dyed scarlet by the murio-sul-
phate of tin, cochineal, and quercitron bark j but
the colour is extremely fugitive.
Of Dyeing Yellow.
The chief yellow dyes are M^eld, sumach, fustic,
turmeric, and quercitron bark.
Weld is a vegetable that grows commonly in
this country.
Sumach is a shrub growing naturally in the
South of Europe.
Fustic is the wood of a tree wliich grows in the
West Indies.
Querciti^on is the bark of a tree which is a native
of North America.
DYEING. 189
It is not possible to give to cloth a permanent
yellow colour without the use of mordants. Alum
is the most usual mordant. TFool is dyed yellow
by weld, by the use of alum and tartar. Quercitron
bark gives nearly the same colour, but more abun-
dantly, and it is rather cheaper than weld. The
process is as follows : boil the cloth for an hour or
more in a solution of alum, and then immerse it in
a bath of quercitron bark. Next add a small quan-
tity of clean powdered chalk, and continue the
boiling for eight or ten minutes. The yellow thus
given will be as good as that obtained from weld.
If very bright yellows are required, the tin mor-
dant must be usedj and sometimes alum is added
to the tin.
If an addition of tartar be made to the mordant,
the yellow will have a slight tinge of green.
If an orange or an aurora be required, a small
portion of cochineal must be added.
Silk used formerly to be always dyed yellow
with weld, but quercitron bark is now found to
answer equally well, and at less expense. The
proportion should be from one to two parts of bark
to twelve pounds of silk, according to the particular
shade of colour wanted. The bark, powdered and
tied up in a bag, should be put into the dyeing
vessel whilst the water is cold, and as soon as it
becomes blood warm, *the silk previously alumed
should also be put in and dyed as usual, and when
the shade is required to be deep, a little chalk or
pearl-ashes may be added towards the end of the
operation.
When very lively yellows are required, a little of
the raurio-sulphate of tin may be employed as a
mordant in addition to the alum. Annotto com-
1§0 byfitNG.
municates an aurora colour to silk, the colour of
the annotto is extracted by means of alcali.
To dye cotton and linen yellow, proceed as fol-
lows. Take a sufficient quantity of the acetate of
alumine, formed by dissolving one pound of sugar
of lead, aiid three pounds of alum, and the cotton
or linen '.eing properly cleansed, immerse it in this
mordant (which ought to be blood warm) for two
hours, let it be then taken out and moderately
pressed or squeezed over a proper vessel, to prevent
the unnecessary waste of the mordant, dry it in a
stove heat, and soak it again in the aluminous mor-
dant; it is then taken out, and again pressed and
squeezed as before ; after which, without being
rinsed, it is thoroughly wetted in as much, and
only as much, lime-water as will conveniently suf-
fice for that purpose, and afterwards dried. The
soaking in the acetate of alumine maybe again re-
peated, and if the shade of yellow is required to be
very bright and durable, the alternate wetting with
lime water and soaking in the mordant may be re-
peated three or four tim.es. Thus a sufficient quan-
titv of alumine is combined with the cloth, and the
combination is rendered more permanent by the
addition of some lime. The dyeing both is pre-
pared by putting 12 or 18 parts of quercitron bark,
(according to the depth of the shade required,) tied
up in a bag, into a sufficient quantity of cold water.
Into this bath the cloth is to be put, and turned
round in it for an hour, while its temperature is
gradually raised to about 120*^, it is then to be
brought to a boiling heat, and the cloth allowed
to remain in it after that only a few minutes. If
it be kept long at a boiling heat, the yellow ac-
quires a shade of brown.
DYEING. 191
To dye nankeen yellow, boil the cotton in a so-
lution of carbonate of potash, and then dip it in a
solution of the red sulphate of iron.
Of Dyeing Blue.
There are but few substances capable of furnish-
ing blue dyes. The only vegetable products are
indigo and wood. Indigo is a rich blue colour
procured from the fecula of a species of plant that
is cultivated in America, and also in the East Indies.
The colouring matter is extracted by water, and is
at first green, but immediately absorbs oxygen,
and then assumes a blue colour. It becomes at
the same time insoluble in water, but is soluble in
sulphuric acid.
As indigo has a very strong affinity for wool, silk,
cotton, and linen, a mordant is unnecessary in dye-
ing with it. The colour is very permanent, because
the indigo being already saturated with oxygen, to
which it owes its blue colour, is little liable to be
decomposed. But it is essential that the indigo
be applied in a state of solution in order to attach
itself to the cloth.
A solution of indigo in the sulphuric acid is used
for dyeing wool ; this is called ScLvon bluet and it
gives a very beautiful colour. But it will not do
for dying cotton or wool, because their affinity for
indigo is not sufficiently great to enable them to
decompose the sulphate of indigo.
To dye by the sulphate of indigo, dissolve oile
})art of indigo in four parts of concentrated sul-
phuric acid ; add to the solution one part of dry car-
bonate of potash, and dilute the whole with eight
times its weight of water. Boil the cloth for an
192 DYEING.
hour in a solution of five parts of alum, and three
of tartar, for every thirty-two parts of cloth. The
clotli is then to be put into a bath of sulphate of
indigo, diluted according to the strength of shade
required, and kept till it has acquired the desired
colour. The use of the alum and tartar is not to
act as mordants, but to facilitate the decomposition
of the indigo. The alcaii is added to the sulphate
for the same reason. Another use of these sub-
stances is, that they protect the cloth from the action
of the sulphuric acid, by neutralizing part of it,
otherwise the texture of the cloth might be
injured.
This, however, is not the most common method o[
dyeing by indigo. The usual method is to deprive
the indigo of the oxygen which has been combined
with the green fecula, and to which it owes its blue
colour, and thus reduce to the green state again.
It is then capable of being dissolved in water by
means of the alcalies or alcaline earths, which act
upon it very readily in that state,
To dye wool blue, indigo is mixed with wood,
bran, and madder, vegetable substances which
readily undergo fermentation ; and the whole is
boiled together, stirring the mixture frequently.
JBy this a fermentation takes place, and the oxy-
gen is separated from the indigo. Quick lime or
alcaii is then tlu'own in, which dissolves the green
base of the indigo. The solution of indigo is apt
to run into the putrid fermentation, which is known
by the putrid vapours whicli it exhales ; the green
colour then disappears, and, indeed, the colouring
matter is decomposed. This danger is prevented
by adding more lime to correct the putrescent
tendency. Sometimes the fermentation does not
proceed with sufficient activity, and then more bran
DYEING. 195
or wood is to be added. Wlien the wool or cloth
is to be put into the indigo vat to be dyed, it
should be wrung out of tepid water, and then in-
troduced into the vat, where it should be kept for a
longer or shorter time according to the strength of
shade required. After being taken out, it is ex-
posed to air, when the green colour which it had
imbibed in the vat is changed to a blue by the
absorption of the oxygen of the atmosphere. It is
then to be carefully washed.
Woad itself contains a colouring matter exactly
similar to indigo, and indigo may be extracted from
it, but the quantity is small.
Cotton and linen are dyed blue by putting the
indigo into a solution of some substance that has
a stronger affinity for oxygen than the green bases
of indigo. Green sulphate of iron, and metallic
sulphurets answer this purpose, the green sulphate
attracts the oxygen from the indigo, and reduces
it to the green state, in which it is dissolved by
lime added to the solution. The cloth is then put
into the bath.
Silk is dyed blue by indigo fermented by bran
and madder, and the indigo dissolved by potash.
If the shade required be dark, it is dyed first with
archill, which is called giving it a ground colour.n
Of dyeing Black.
The substance that produces the black dye is the
ta nno'gallate oi'h'on. Decoctions of many vege-
tables strike a black with a solution of the red
oxide of iron. Of these nut-galls give the most
copious precipitate.
Logwood is generally employed as an auxiliary,
because it communicates lustre, and adds consider-
VOL. II. O
19*4 DYEING.
aljly to the fullness of the black. The decoction
of logwood which is reddish becomes black by
sulphate of iron.
To dye cloth or wool black, the first process
generally is to dye it blue, which renders the black
to be given more intense. If the cloth be coarse,
and the blue dye too expensive, a brown dye may
be given by means of walnut peels. It is then
boiled for two hours in a decoction of nut galls,
and then for two hours more in a bath composed
of logwood and sulphate of iron, at a scalding heat,
but not boiled. During the operation, it must be
frequently exposed to the air. The common pro-
portion are five parts of galls, five of sulphate of
iron, and thirty of logwood, for every 100 of cloth.
For coarse cloths the previous blue dye is omitted.
The cloth is then washed and fulled.
Silk is dyed black as follows. After boiling it
with soap, it is galled, and afterwards washed. It
combines with a considerable portion of the astrin-
gent principle, and increases in weight. It is then
dipped into a bath of sulphate of iron and gum
arable.
Cotton and I'men are first dyed blue, then steeped
in a decoction of galls, and alder bark. It is then
put into a batli of acetite of iron, taken out and
exposed to the air. This operation is repeated
several times.
Of dyeing Compotincl Colours.
Compound colours are produced either by mix-
ing together two or more simple ones, or by dyeing
cloth first one simple colour and afterwards
another.
Greens are formed of blues and yellows. Wool
is dyed green by dyeing it first blue of a depth of
shade sufficient for the required kind of green. It
is then washed and boiled in a bath of weld and
tartar, or any of the processes used for dyeing blue
and yellow may be used. Various shades will be
given by different proportions of the dyeing ma-
terials. The green called Saa:on gren? is obtained
by solutions of indigo in sulphuric acid, sometimes
quercitron bark is used. Another process for
Saxon green is by the quercitron bark, and then a
bath of the murio-sulphate of tin and alum with
sulphate of indigo.
Purples, violets. Sec. — All the shades of these
colours are formed of blue and red. Sometimes
the cloth is dyed blue and then scarlet, and some-
times cochineal is mixed with sulphate of indigo,
and the purple dyed at once. Silk is dyed first by
cochineal and afterwards by indigo. Cotton and
linen are dyed blue, then galled, and boiled in
loffwood. li ,, .,"
Orange colours are produced by mixtures of
yellow and red. Wool is first dyed scarlet and
then yellow.
Olive is blue combined with red and yellow.
Cinnamon colour is given to wool by dyeing it
first with madder, then yellow. Silk is dyed the
same colour by logwood. Brazil-wood, and fustic.
Cotton and linen receive a cinnamon colour by
weld and madder.
Brown is given to cloth by quercitron bark, or
by walnut peels.
When walnut peels, or the green covering of the
walnut, are first separated, they are white internally,
but soon assume a brown or even a black colour
on exposure to the air. They readily give up their
0 ^
196 CALICO PRINTING.
colouring matter to water. It is common to keep
them in water for a year before they are used.
Wool is dyed brown with them by steeping in a
decoction for a length of time proportioned to the
depth of colour required. The same colouring
matter is found in the root of the walnut-tree, but
in smaller quantity. Other trees, as the bark of the
birch may be used for dyeing browns, and in these
cases it is probable that the colouring matter is
combined with the tanning principle, and this may
be the reason why no mordant is necessary, both
the cloth and colouring matter having a strong
affinity for tannin.
Drab colours are dyed by combining brown
oxide of iron with the cloth, and then the yellow
of quercitron bark. The strength of shade will be
more or less, by varying the quantity of the mor-
dant, w^hen the proportion is small the colour in-
clines to olive or yellow, on the contrary the drab
may be deepened or saddened, as the dyers term
it, by mixing a little sumach with the bark.
CALICO PRINTING.
Calico isa species of cotton cloth ornamented with
coloured patterns. The name is derived from Cali-
cut, a district of India, where it was first made, and
from whence it was formerly imported. The art
of making calicoes had been practised there from
time immemorial, but it is scarcely, a hundred
years since it was known in Europe; it has al-
ready risen to such perfection as to equal if not
exceed the manufactures of India, in the elegance
of the patterns, the beauty and permanance of the
colours, and the expedition with which the different
operations are carried on.
CALICO PRINTING. 197
The process of calico-printing consists in impreg-
nating those parts of the cloth which are to receive
the coloured pattern with a mordant, and then dye-
ing the cloth by the usual methods. The dye is
firmly fixed to that part only where the mordant
has been applied ; and, although the whole cloth
has received the tint, yet the colour will be easily
discharged from the unmordanted parts by washing,
and exposing on the grass to the sun and air for
some days with the wrong side uppermost. Thus,
suppose a pattern had been applied to white cloth
with a solution of acetite ofalumine, and that then
the whole was dyed with madder ; when taken out
of the dye-vat the whole cloth would be red ; but,
by washing and bleaching, the madder will be dis-
charged from every part of the cloth except where
the acetite ofalumine had been applied ; and, con-
sequently, the pattern alone will appear red. In
the same manner the patterns may be applied of
any other colour by varying the dye, as quercitron
bark or weld for yellow, &c.
Two mordants are particularly employed in ca-
lico-printing, acetite of alumine, and iron dissolved
in some vegetable acid.
The acetite of alumine is made by a double de-
composition of alum and sugar of lead. When iron
is used as a mordant, it is dissolved in vinegar,
soured beer, or pyroligneous acid ; and it is, there-
fore, an acetite of iron mixed with a portion of tar-
trite, gallate, and, perhaps, other salts of the metal.
When the colour of the required pattern varies
in different places, this effect is produced on the
cloth, by impregnating the several parts with vari-
ous mordants. Thus, if one part is printed with
acetite ofalumine, and another with acetite of iron,
o 3
1^ CALICO PRINTING.
and the whole cloth afterwards dyed with mad-
der and bleached, tlie pattern will appear in
red and brown.
The mordants are applied to the cloth either by
a pencil, or by means of blocks on which the pat-
tern is cnt. Care must be taken that the printing
from the block does not spread, or that the impres-
sions from the several blocks do not interfere with
one another when more than one is apphed. For
this purpose it is necessary, that the substance used
as mordants should have a degree of consistence
that may prevent them ft'om spreading. Flour
paste, or starch, is mixed with the mordant when it
is applied by blocks, and gum arable when it is
but on by a pencil. This thickening reqiiires exact-
ness : if too little is used, the pattern will spread ;
and, if too much, the cotton will not receive a suf-
ficient quantity of the mordant, and will take the
dye imperfectly.
In order that the impression given by the blocks
with the mordant may be seen easily before it is
dyed, the mordant is tinged with some colouring
matter that wdll not remain fixed. Decoction of
Brazil-wood is used for this purpose.
Before printing, the cotton cloth is well bleached
and calendered, and laid smooth on a table : the
blocks are applied by hand, and struck with a
mallet. The cotton is then dried well in a room
with a stove, which not only fixes the mordant
more securely, but drives off part of the acetous
acid from its base, by which the mordant will com-
bine in a greater proportion, and more intimately
with the cloth.
To discharge the paste and gum used with the
mordant, the cloth is next to be washed with warm
CALICO PRINTINe. 199
water and cow-dung ; this, also, discharges such
parts of the mordant as are not properly fixed,
enough being still left to fix the dye. The cloth
is then rinsed in clear water. It is then dyed in
the usual manner.
The principal dye-stuffs used by calico-printers
are indigo, madder, quercitron bark, and weld.
After dyeing, the cloth is well washed, exposed
on the grass, and bleached ; by which all the parts
not touched by the mordant are restored to their
original whiteness.
In this manner various colours may be given by
one dyeing, merely by varying the mordant. Thus,
if one pattern be printed with alum alone, a second
with a mixture of alum and iron liquor, a third
v.'ith iron liquor alone, and a fourth with iron li-
quor and galls, and the piece be afterwards dyed
with quercitron or weld, and the ground bleached
in the usual manner ; the first pattern will be pure
yellow, the second will be olive, the third of a dark
drab colour, and the fourth nearly black, while
the ground will be white.
As indigo does not require any mordant, it is
applied at once, either by a pencil or by a block
and paste. But, as has been mentioned under dye-
ing, indigo will not combine with the cloth except
in its disoxygenated or green state ; and, if applied
thus by the pencil, it would return to the blue state
before it had time to fix upon the stuff. The in-
digo is, therefore, prepared by boiling with potash,
made caustic by quicklime, to which is added
orpiment for the disoxygenation of the indigo.
This solution is thickened with gum. It must be
excluded from the air, otherwise it would attract
oxygen and return to the blue or insoluble state.
Dr. Bancroft proposed substituting brown sugar
o 4 . .
500 CALICO PRINTING.
for orpiments, as it is equally efficacious in disoxy-
genating the indigo, and will also serve instead
of gum.
Some calicoes are printed only with one colour ;
others have two ; others three, or more, even to
the number of eight, ten, or twelve. The smaller
the number of colours, the fewer are the processes.
To give an example where six colours are used.
1. A nankeen yellow, of various shades down to
a deep yellowish brown or drab, is given by acetite
of iron put on with gum or paste, and afterwards
plunged into the potash ley.
2. Yellow, by a mordant of acetite of alumine,
the dyeing by quercitron bark and bleaching.
3. Red, by the last process, only madder is sub-
stituted for the bark.
4. Light blue is given by making a block for all
those parts that are to be white, and printing by
it on the cloth a composition of which wax is the
principal ingredient, or pipe- clay and paste. The
cloth is then dyed in a cold indigo vat, and the
wax removed by hot water.
5. Lilac flea-brown, and blackish brown, are
given by acetite of iron, and dyeing afterwards
with madder.
6. Dove-colour and drab, by acetite of iron and
quercitron bark.
The same mordant will frequently do tor several
colours. Thus, suppose one part of the cloth
should be printed with acetite of alumine, another
with acetite of iron, and a third with a mixture of
these two mordants, and the whole afterwards dyed
with quercitron bark ; then the following colours
would appear, viz. yellow, drab, olive ; and various
depths of shade will be given by varying the pro-
portions ot" iron in the mordant.
TANNING, 201
If some parts of the yellow be covered over with
the indigo liquor, applied with a pencil, it will be
converted into green. By the indigo, also, any
parts that are required to be blue may be pencilled.
If j instead of quercitron bark, the cloth printed
with the three mordants just mentioned be dyed
with madder, then the colours exhibited will be
red, brown or black, and purple.
Other processes are still more complicated when
a great number of colours are required. New
mordants are applied to parts of the pattern alrea-
dy printed, and the cloth again dyed, by which
those parts only receive a new colour.
Sometimes the dye stuff and the mordant are
mixed together in the first instance, and printed on
the cloth, which is a great saving of time and ex-
pense ; but the colours thus produced on the cloth
are not permanent: washing, or even exposure to
the air frequently destroys them.
TANNING.
Tanning is the art of converting the raw skins of
animals into leather.
The skin is composed chiefly of two parts, a thin
white elastic layer on the outside, which is called
the epidermis, or cuticle ; and a much thicker layer,
composed of a great many fibres, closely inter-
woven, and disposed in different directions: this
is called the cutisy or true skin.
The epidermis is that part of the skin which is
raised in blisters. It is easily separated from the
cutis by maceration in hot water. It possesses a
very great degree of elasticity. It is totally inso-
lubje in water and alcohol. Pure fixed alcalis dis-
solve it completely, as does lime likewise though
slowly.
S02
TANNING.
When a portion of cutis is macerated for some
hours in water, with agitation and pressure, the
blood, and all the extraneous matter with which it
was loaded, are separated from it, but its texture
remains unaltered. On evaporating the water em-
ployed, a small quantity of gelatine may be ob-
tained. No subsequent maceration in cold water
has any farther effect ; the weight of the cutis is
not diminished, and its texture is not altered ; but
if it be boiled in a sufficient quantity of water, it
may be completely dissolved, and the whole of it,
by evaporating the water, obtained in the state of
gelatine.
It was mentioned, when treating of chemistry,
that gelatine wdth tannin^ or the tanning principle o^
vegetables, formed a combination, which is inso-
luble in water. Upon this depends the art of
making leather ; the gelatinous part of the skin
combining with the tannin of the bark usually
employed.
The process which has long been used in this
country is as follows ; the leather tanned in Eng-
land consists chiefly of three sorts, known by the
name o^ butts or backs, hides, and skins. Butts are
generally made from the stoutest and heaviest ox
hides, and are managed as follows : after the horns
are taken off, tlie hides are laid smooth in heaps for
one or two days in the summer, and for five or six
in the winter ; they are then hung on poles, in a
close room called a smoke-house, in which is kept
a smouldering fire of wet tan ; this occasions a
small degree of putrefaction, by which means the
hair is easily got offj by spreading the hide on a
sort of wooden horse or beam, and scraping it with
a crooked knife. The hair being taken off, the
hide is thrown into a pit or pool of water, to
TANNING. 203
cleanse it from the dirt, &c. which being done, the
hide is again spread on the wooden beam, and the
grease, loose flesh, extraneous filth, &c. carefully
scrubbed out or taken off; the hides are then put
into a pit of strong liquor, called ooze^ prepared in
pits kept for the purpose, by infusing ground bark
in water ; this is termed colouring ; after which
they are removed into another pit called a scower-
ing, which consists of water strongly impregnated
with vitriolic acid, or with a vegetable acid, prepared
from rye or barley. This operation (which is called
raising)^ by distending the pores of the hides, occa-
sions them more readily to imbibe the ooze, the ef-
fect of which is to combine with the gelatinous part
of the skin, and form with \i leather. The hides are
then taken out of the scowering, and spread smooth
in ai pit commonly filled with water, called a binder,
with a quantity of ground bark strewed between
each. After laying a month or six weeks, they are
taken up ; and the decayed bark and liquot being
drawn out of the pit, it is filled again with strong
ooze, when they are put in as before. With bark
between each hide. They now lie two or thi^e
months, at the expiration of which the saitie oper-
ation is repeated ; they then remain four or five
months, when they again undergo the same process,
and after being three months in the last pit, aTe com-
pletely tanned; unless the hides are so remarkably
stout as to want an additional pit or layer. The
whole process requires from eleven to eighteen
months, and sometimes two years, according to the
substance of the hide, and discretion of the tanner.
When taken out of the pit to be dried, they are
hung on poles, and after being compressed by a
steel pin, and beat out smooth by wooden hammers,
called hattSy the operation is complete ; and when
204 T4.NNING.
thoroughly dry, they are fit for sale. Butts are
chiefly used for the soles of stout shoes.
The leather which goes under the denomination
of hideSj is generally made of cow hides, or the
lighter ox hides, which are thus managed. After
the horns are taken off, and the hides washed, they
are put into a pit of water, saturated with lime,
where they remain a few days, when they are taken
out, and the hair scraped off on a wooden beam, as
before described ; they are then washed in a pit,
or pool of water, and the loose flesh, &c. being
taken off, they are removed into a pit of weak
ooze, where they are taken up, and put down
(which is technically termed handling') two or
three times a-day, for the first week ; every second
or third day they are shifted into a pit of fresh
ooze, somewhat stronger than the former ; till at
the end of a month or six weeks they are put into
a strong ooze, in which they are handled once or
twice a-week with fresh bark for two or three
months. They are then removed into another pit,
called a layer, in which they are laid smooth, with
bark ground very fine, strewed between each bide.
After remaining here two or three months, they
are generally taken up, when the ooze is drawn out,
and the hides put in again with fresh ooze and
fresh bark, where, after lying two or three months
more, they are completely tanned, except a few
very stout hides, which may require an extra layer:
they are then taken out, and hung on poles, and
being hammered and smoothed by a steel pin, are,
when dry, fit for sale. These hides are called crop
hides ; they are from ten to eighteen months in
tanning, and are used for the soles of shoes.
Skins is the general term for the skins of
calves, seals, hogs, dogs, &c. These, after being
TANNING. 205
washed in water, are put into lime pits, as before
mentioned, where they are taken up and put down
every third or fourth day, for a fortnight or three
weeks, in order to destroy the epidermis of the
skin. The hair is then scraped off, and the excres-
cences being removed, they are put into a pit of
water impregnated with pigeon dung, called a
grainer, forming an alcaline ley, which in a week
or ten days soaking out the lime, grease, and sa-
ponaceous matter (during which period they are
several times scraped over with a crooked knife, to
work out the dirt and filth), softens the skins, and
prepares them for the reception of the ooze. They
are then put into a pit of weak ooze, in the same
manner as the hides, and being frequently handled,
are by degrees removed into a stronger, and still
stronger liquor, for a month or six weeks, when
they are put into a very strong ooze, with fresh
bark ground very fine, and at the end of two or
three months, according to their substances, are
sufficiently tanned : when they are taken out,
hung on poles, dried, and are fit for sale. These
skins are afterwards dressed and blacked by the
curriers, and are used for the upper leathers of
shoes, boots, &c.
The lighter sort of hides, called dressing hides,
as well as horse hides, are managed nearly in the
same manner as skins ; and are used for coach-
work, harness work, &c. &c.
As the method of tanning above described, and
all others in general use, are extremely tedious and
expensive in their operation, various schemes at
different times have been suggested to shorten the
process, and lessen the expense.
Much hght has been thrown by modern che-
mists upon the theory of tanning, and considerable
2015 TANNINE .
improvements have been made in the practice of
this art. M. Seguin, in France, has particularly
distinguished himself by his researches on thissu]b-
ject, and mucli improved the art in his country.
In 179<5, Mr. William Desmond obtained a patent
for practising Seguin's method in England. He
obtained the tanning principle, by digesting oak
bark, or other proper material in cold water, in an
apparatus nearly similar to that used in the salt-
petre works : that is to say, the water which has
remained upon the powdered bark for a certain
time, in one vessel, is drawn off by a cock, and
poured upon fresh tan: this is again to be drawn
off, and poured upon other fresh tan ; and in this
way the process is to be continued to the fifth
vessel. The liquor is tlien highly coloured, and
and marks from six to eight degrees upon the hy-
drometer for salts. This he calls the tanning lix-
ivium.
The criterion for ascertaining its strength is the
quantity of the solution of gelatine which a given
quantity of it will precipitate. Isinglass is used
for this purpose, being entirely composed of ge-
latine. And liere it may be observed, that this is
the mode of ascertaining the quantity of tanning
principle in any vegetable substance, and, conse-
quently, how far they may be used as a substitute
for oak bark.
The hides, after being prepared in the usual way,
are immersed for some hours in a weak tanning lix-
ivium of only one or two degrees ; to obtain which,
the latter portions of the infusions are set apart, or
else some of that which has been partly exhausted
by use in tanning. The hides are then to be put
into a stronger lixivium, where, in a few days, they
will be brought to the same degree of saturation
TANNING. 207
with the liquor in which they are immersed. The
strength of the hquor will by this means be consi-
derably diminished, and must, therefore, be renew-
ed. When the hides are by this means completely
saturated, that is to say, perfectly tanned, they
are to be removed, and slowly dried in the shade.
It has been proposed to use the residuum of the
tanning lixivium, or the exhausted ooze (which
contains a portion of Gallic acid, this forming a
constituent part of astringent vegetables), for the
purpose of taking off the hair ; but tliis liquor
seems to contain no substances capable of acting
upon the epidermis, or of loosening the hair ; and
when skin is taken off by being exposed to it, the
effect must really be owing to incipient putre-
faction.
The length of time necessary to tan leather
completely, according to the old process, is cer-
tainly a very great inconvenience ; and there is no
doubt but that it may be much shortened by fol-
lowing the new method. It has been found, how-
ever, that the leather so tanned has not been so
durable as that which has been formed by a slower
process.
The public is much indebted to Sir Humphry
Davy, for the attention which he has paid to this
subject. From his excellent paper " On the Con-
stituent Parts of Astringent Vegetables,'* in the
Philosophical Transactions, we present the reader
with the following extract.
" In considering the relation of the different
facts that have been detailed, to the processes of
tanning and of leather-making, it will appear suf-
ficiently evident, that when skin is tanned in as-
tringent infusions that contain, as well as tannin,
extractive matters, portions of these matters enter,
208 TANNING.
with the tannin, into chemical combination with
the skin. In no case is there any reason to beUeve
that galUc acid is absorbed in this process ; and M.
Seguin's ingenious theory of the agency of this
substance, in producing the de-oxygenation of
skin, seems supported by no proofs. Even in the
formation of glue from skin, there is no evidence
which ought to induce us to suppose that it loses a
portion of oxygen ; and the effect appears to be
owing merely to the separation of the gelatine,
from the small quantity of albumen with which it
was combined in the organized form, by the sol-
vent powers of water.
*' The different qualities of leather made with
the same kind of skin, seem to depend very much
upon the different quantities of extractive matter it
contains. The leather obtained by means of in-
fusions of galls, is generally found harder, and more
liable to crack, than the leather obtained from the
infusion of barks ; and in all cases it contains a
a much larger proportion of tannin, and a smaller
proportion of extractive matter.
" When skin is very slowly tanned in weak so-
lutions of the barks, or of catechu, it combines with
a considerable proportion of extractive matter ; and
in these cases, though the increase of weight of the
skin is comparatively small, yet it is rendered per-
fectly insoluble in water, and is found soft, and at
the same time strong. The saturated astringent
infusions of barks contain much less extractive
matter, in proportion to their tannin, than the weak
infusions; and when skin is quickly tanned in
them, common experience shows that it produces
leather less durable than the leather slowly formed.
** Besides, in the case of quick tanning by means
of infusions of barks, a quantity of vegetable ex-
TANNING. 209
tractive matter is lost to the manufacturer, which
might have been made to enter into the composi-
tion of his leather. These observations show, that
there is some foundation for the vulgar opinion of
workmen, concerning what is technically called
the feeding of leather in the slow method of tan-
ning J and though the processes of the art may in
some cases be protracted for an unnecessary length
of time, yet, in general, they appear to have ar-
rived, in consequence of repeated practical expe-
riments, at a degree of perfection which cannot be
very flir extended by means of any elucidations of
theory that have as yet been known.'*
As a vast quantity of bark may easily be ob-
tained in countries that are covered with natural
forests, such as many parts of America, New Hol-
land, &c. it has been suggested, as a method of
lessening the expense of freight in bringing it over,
to make an extract from the bark, which might be
very easily transported, and which would serve the
purpose of the tanner as well as the bark itself.
It was first suspected by Sir Joseph Banks, and
afterwards confirmed by the experiments of Sir
Humphry Davy, that a substance called catechu, or
terra Japonica, brought from the East Indies, con-
tained a vast quantity of tannin ; so much so, that
it far excels every other known substance in this
respect, Onepoun.-l of catecliu contains as much
tannui as eight or ten pounds of common oak bark,
and would consequently tan proportionately as
much more leather. It is an extract made from the
wood of a species of mimosa, by decoction and sub-
sequent evaporation.
Oak bark being a very expensive article in the
process of tanning, various substances have been
proposed as substitutes for it. All the parts of ve-
VOL. ]I, p
210 TANNING.
getables which are of an astringent nature, contain
tannin (which may be known by their giving preci-
pitates with gelatine, insoluble in water), and will
answer this purpose. The leaves, branches, fruit,
flowers, of a vast number of plants; every part of the
oak, as the leaves and acorns, oak saw-dust, and the
barks of almost all trees, contain more or less tannin.
Mr. Biggins made a great many experiments
upon the quantity of tanning principle in various
barks, from which he constructed the following
table.
Tanning
principle (in grains\
from half a pint of infusion
and an ounce of solution of
glue.
^
Bark of elm, -
-
28 '
oak, cut in winter,
-
30
horse-chesnut,
.
30
beech.
.
31
willow (boughs)
-
31 1
elder.
-
41 *
plum-tree,
-
58
willow (trunk).
-
52
sycamore.
-
53
birch,
-
54>
cherry-tree.
•
59
saUow,
-
59
mountain-ash.
-
60
poplar.
-
76
hazel.
-
79
ash, -
-
82
Spanish chesnut.
-
98
smooth oak, -
-
104
oak, cut in spring.
-
108
Huntingdon, or Leices-
.
tershire willow.
-
109
sumach,
-
158
mi
CURRYING.
The art of currying consists in rendering tarinetl
skins supple and of uniform density, and iiiipregr
nating them with oil, so as to render them in a
great degree impervious to water.
The stronger and thicker hides are usually em-?
ployed for making the soles of boots r.nd shoes, and
these are rendered fit for their several purposes by
the shoemakers after they are tanned ; but suph
skins as are intended for the upper leathers ^nd
quarters of shoes, for the legs of boots, for coach
find harness leather, saddles, and other things, must
be subjected to the process of currying.
These skins after coming 'from the tanners, hav-
ing many fleshy fibres on them, are well soaked in
common water. They are then taken out aqcj
stretched upon a very even wooden horse ; where
with a paring knife all the superfluous flesh is
scraped ofi\ and they are again put into soak. After
the soaking is completed the currier takes them
again out of the water, and having stretched them
out, presses them with his feet, or a flat stone fixed
in a handle, to make them more supple, and to press
out all the filth that the leather may have acquired
in tanning, and also the water it has absorbed in
soaking.
The skins are next to be oiledf to render them
pliant and impervious to wet. After they are half
dried, they are laid upon tables, and first the grain
side of the leather is rubbed over with a mixture
of fish oil and tallow ; then the flesh side is im-
pregnated with a large proportion of oil. After
having been hung up a sufficient time to dry, they
are taken down and rubbed, pressed, and folded in
various directions, and then spread out, when th^Y
p 2
Sl^ MANUFACTURE OF SODA,
are rolled with considerable pressure upon both
sides with a fluted board fastened to the operator's
hand by a strap ; by this means, and by repeating
the rolling, a grain is given to the leather.
After the skins are curried, it may be required
to colour them. The colours usually given to
them are black, white, red, green, yellow, &c.
If the skins are to be blacked, the process varies
according: to the side of the skin to be coloured.
Leather that is to be blacked on the flesh side,
which is the case with most of the finer leather
intended for shoes and boots, is coloured with a
mixture of lamp black, oil, and tallow, rubbed into
the leather. And what is to be coloured on the
grain side is done over with chamber lye, and then
with a solution of sulphate of iron, which turns it
black.
MANUFACTURE OF SODA.
Soda, or the mineral alcali, (described above,
under Chemistry) is sometimes found in a native
state, as in the lakes of Natron in Egypt, which are
dry in the summer season ; the water leaving after
evaporation a bed of soda, or, as it is there called,
natron, of two feet in thickness.
A marine plant, called the Salsola soda, whicli
grows among the cliffs on the sea coast, seems to be
endowed by nature with the property of decom-
posing the salt water, that is, of separating the
muriatic acid from the soda, which latter it absorbs.
This plant is collected by the Spaniards with great
care, and burnt for the manufacture of barilla,
which is a carbonate of soda mixed with various
impurities.
Soda is also procured in a still more impure
state, by the burning of the sea weeds on our own
MANUFACTURE OF SODA. 213
shores, particularly in Scotland, from which is pro- j
duced a substance called help.
But the demand for a pure carbonate of soda
having become very considerable of late years, from
its great utility in many arts and processes, various
means have been tried for procuring it by decom-
posing the salts, in which it exists, combined with
acids. Muriate of soda has been decomposed for
this purpose. The following method is described
in Nicholson's Journal.
Solutions of 500lbs. of sulphate of soda*, and
560lbs. of American potash, are made to boil, and
are then mixed. As soon as the mixture boils, it
is conveyed into a cistern of wood, lined with lead,
half an inch thick, which is fixed in a cool place.
Sticks of wood are then placed across the cistern,
from which slips of sheet lead, two or three inches
wide, are hung into the fluid, at four inches distance
from each other. When all is cool, the fluid is let
off, and the chrystallized salt is detached from the
slips of lead, and the bottom of the trough. The
salt is then washed, to free it from impurities, after
which it is transferred again into the boiler, dis-
solved in clear water, and evaporated by heat. As
soon as a strong pellicle is formed, it is suffered to
cool so far that the hand may be dipped into it
without injury, and the heat is kept at that temper-
ature as long as effectual pellicles continue to be
formed over the whole surface of the boiler, and
then fall to the bottom. When no more are formed,
the fire is withdrawn, and the fluid ladled out into
the cistern to crystallize. The sulphate of potash,
&c. which had been deposited, is then taken out of
* Sulphate of soda is sold cheap by the bleachers, who save
it as the residue in decomposing common salt by sulphuric acid
with manganese.
p 3
2l4i MAKtl^ACTUilE of POTASH.
the boiler, and put aside. By this process from 136
to lo9lbs. of soda may be obtained from 1 OOlbs. Of
sulphate of soda.
MANUFACTURE OF POTASH.
Potash, or the fixed vegetable alcali, exists as an
ingredient, in very small quantity, in many mine-
rals. It is also obtained from the tartar, or from
lees of Wine, in which it is called salt of tartar.
But the great supply of this substance is procured
from the ashes of burnt vegetables.
In many districts of England and Ireland they
burfii the common fern to ashes, which they mould
up with a little water, into balls of about three or
foiir inches in diameter ; these are called ash balls,
and are the rudest preparation of this alcali.
. The potash of commerce, or Mack potash, i(s
always procured from the combustion of wood, and
can, therefore, only be made in those countries where
wood is very plentiful^ as Poland, Russia, and Ger-
manyw This country is chiefly supplied from Ame-
rica. The ashes of burnt wood are put into a
cistern with water^ and a strong lixivium is made.
After a time, tlie water, holding the alcali in solu-
tion, is drawn oflj leaving the impurities behind.
Potash is converted into a purer state by calcining
it in a reverberatory furnace. It becomes then dry,
poix)us, considerably caustic, extremely deliques-
cent, and of a beautiful bluish colour, from which
it is called pearl ash.
All these are carbonates of potash.
To obtain potash in a state of perfect purity, or
uncombined with carbonic acid, the carbonate must
be boiled with twice its weight of quicklime to de-
REFINING METALS. 515
prive it of the carbonic acid ; then to free it from
other impurities, it must be dissolved in spirits of
wine, (which dissolves alcalis and no other salt) and
the solution evaporated to dryness. It is then pure
and powerfully caustic.
REFINING METALS.
The term refining signifies the purification of
some substance : but we mean to confine it at pre-
sent to the separation of gold, silver, and copper
from each other, and obtaining each of them in a
pure state.
Cupellation.
Gold and silver being the only metals capable of
withstanding the action of very strong heat, are
therefore called perfect metals. All other metals
are reduced to the state of oxides when exposed to
a violent fire with access of air. Gold and silver
may, therefore, be purified from all the baser metals
by keeping them fused till the alloy be destroyed :
but this process would be very expensive, from the
great consumption of fuel, and would be exceed-
ingly tedious. A shorter and more advantageous
method of performing this operation has been dis-
covered.
A certain quantity of lead is added to the alloy
of gold and silver, and the whole is exposed to the
action of the fire.
Lead is one of the metals which is most quickly
converted by heat into an oxide, which is easily
melted into a semi- vitrified, and powerful vitrifying
matter, called litharge. By increasing the proportion
of imperfect metals, it prevents them from being so
p 4
216 CUPELLATION.
well covered and protected by the perfect metals j
and by uniting with these imperfect metals, it com-
municates to them its property of being very easily
oxidated. By its vitrifying and fusing property,
which it exercises with all its force upon the cal-
cined and naturally refractory parts of the other
metals, it facilitates and accelerates the fusion, sco-
rification, and separation of these metals. The lead,
which in this operation is scorified, and scorifies
along with it the imperfect metals, separates from
the metallic mass with which it is then incapable of
remaining united. It floats upon the surface of the
melted mass, and becomes semi-vitrified. But the
litharge so produced would soon cover the melted
metal, and by preventing the access of air would
prevent the oxidation of the remaining imperfect
metals. To remedy this, such vessels are employed
as are capable of imbibing and absorbing in, their
pores, the melted litharge, and thus remove it out
of the way ; or, for large quantities, vessels are so
constructed, that the fused litharge, besides being
soaked in, may also drain off, through a channel
made in the corner of the vessel.
Experience has shown that for this purpose, ves-
sels made of lixiviated wood or bone-ashes are most
proper. These vessels are called cupels^ and this
process is called cupellation. The cupels are flat
and shallow. The furnace ought to be vaulted,
that the heat may be reverberated upon the sur-
face of the metal during the whole time of the
operation. Upon this surface a crust or dark
coloured pellicle is continually forming. In the
instant when all the imperiect metal is destroyed,
and, consequently, the scorification ceases, the sur-
face of the perfect metal is seen, and appears clean
and brilliant. This forms a kind of fulguration, or
i
REFINING METALS. 217
corruscation, called lightning. By this mark the
metal is known to be refined.
Purification of gold by a7itimony.
When gold contains only a small quantity of alloy,
it may be separated from them by melting it in a
crucible that will hold twice its quantity at least, and
throwing upon it, whilst in fusion, twice its weight
of crude antimony (sulphuret of antimony). The
crucible is then to be covered, and the whole is to
be kept in a melting state for some minutes ; and
when the surface sparkles, it is quickly to be
poured into an inverted cone, which has been pre-
viously heated and greased. By striking the cone
on the ground, the metal will come out when cold.
The compact mass consists of two substances ; the
upper part is the sulphur of the crude antimony,
united with the impure alloy ; and the lower part
is the gold, united to some of the regulus of anti-
mony, proportionable to the quantities of metals
which have been separated from the gold, which
are now united with the sulphur of the antimony.
This regulus of gold may be separated from the
regulus of antimony by simple exposure to less
heat than will melt the gold, because antimony is
volatile in such a heat, and is then dissipated. If
the gold is not sufficiently purified by this first pro-
cess (which is often the case,) it must be repeated
a second, and even a third time. When a part is
dissipated, more heat is required to keep the gold
in fusion ; therefore, the fire must be increased to-
wards the end of the operation. The purification
is completed by means of a little nitre thrown into
the crucible, which effectually calcines the remain-
ing regulus of antimony. Sometimes, after these
218 PARTING.
operations, the gold is found to be deprived of much
of its usual ductility ; this however is easily re-
stored to it, by fusing it with nitre and borax.
The first part of this process is founded on a pro-
perty of sulphur, by which it is incapable of
uniting with gold, and is strongly disposed to unite
with all other metalUc substances, excepting pla-
tina and zinc ; and also upon the property of sul-
phur, that it has less affinity with regulus of anti-
moiiy than with any metallic substance with which
it can unite. Hence, when gold, alloyed with
^Iver, copper, iron, lead, &c. is fused together with
sulphuret of antimony, these latter metals unite
witli the sulphur of the antimony, while the regu-
litm part, disengaged from them by its sulphur,
unites with the gold.
The sulphur of the antimony, though it unites
with the baser metals, does not destroy them, but
forms with them a scoria, from which they may be
separated by treatment as an ore.
Parting.
When the quantity of silver united to the gold
is considerable, they may be separated by other
processes. Nitric acid, muriatic acid, and sulphur,
which cannot dissolve gold, attack silver very
easily ; and, therefore, these three agents furnish
methods of separating silver from gold, which
operation is called parting.
Parting by nitric acid is the most convenient,
and, therefore, most used ; and is even almost the
only one employed by goldsmiths and coiners.
Wherefore it is called simply, parting. That made
with muriatic acid is only made by cementation,
and is known by the name oi' concentrated parting.
PARTING. 219
Lastly, parting by sulphur is made by fusion, and
is, therefore, called dry parting.
Parting gold from silver by iiitric acid or aqua
j^Wf^.— Although parting by nitric acid be easy, it
cannot succeed, or be very exact, unless we attend
to some essential circumstances. The gold and
silver must be in a proper proportion ; for if the
gold be irl too great a quantity-, the silver would be
covered and guarded by it from the action of the
acid ; therefore, when assayers do not know the pro-
portion of gold to silver in the mass, they rub the
mass upon a touch-stone (which is usually composed
of black basalt, though black pottery will do
very weil^) so as to leave a maiiv upon it; they
then make similar marks with the proof-needles,
(which are needles composed of gold and silver
alloyed together in graduated proportions,) and by
comparing the colour of the several marks, they
discover the probable sicaie of admiJiture.
If the trial shows that in any given mass the
silver is not to the gold as three to one, this mass
is improper for the operation of parting by aqua
fortis. In this case, tiie quantity of silver neces-
sary to make any alloy of that proportimi must be
added. This operation is called quart<ition, be-
cause it reduces the gold to a fourth of the whole
mass. No inconvenience arises from too great
quantity of silver, except a waste of aqua fortis.
The nitric acid, or aqua fortis employed, must be
very pure, and especially free from mixture of sul-
phuric and muriatic acids. Its purity must, there-
fore, be ascertained; and if this be found not suffi-
cient, the acid must be purified by nitrate of silver.
If the purity of the nitric acid W' ere not attended
to, a quantity of silver proportionable to these two
foi^eign acids, would be separated during the solu-
220 PARTING*
tion ; and this portion of silver converted by these
acids to sulphate of silver, and to muriate of silver,
would remain mingled with the gold.
When the metallic mass is properly alloyed, it is
to be reduced to plates rolled up spirally, called
cornetSy or to grains. These are to be put into a
matrass, and upon them a quantity of aquafortis is
to be poured, the weight of which is to that of the
silver as three to two ; and as the nitric acid em-
ployed for this operation is rather weak, the solu-
tion is assisted, especially at first, by the heat of a
sand-bath, in which the matrass is to be placed.
When, notwithstanding the heat, no further mark
of solution appears, the aqua fortis charged with
silver is to be decanted. Fresh nitric acid is to be
poured into the matrass, stronger than the former,
and in less quantity, which must be boiled in the
remaining mass, and decanted as the former.
Aqua fortis must even be boiled a third timex)n the
remaining gold, that all the silver be certainly dis-
solved. The gold is then to be washed with boil-
ing water. This gold is very pure, if the operation
has been performed with due attention. It is called
gold of parting.
The silver dissolved in the aqua fortis may be
separated either by distillation — in which case all
the aqua fortis is recovered very pure, and fit for
another parting — or it may be precipitated by some
substance which has a greater affinity than this
metal with nitric acid. Copper is generally em-
ployed for this purpose in the mint.
The solution of silver is put into copper vessels.
The aqua fortis dissolves the copper, and the silver
precipitates. When the silver is all precipitated,
the new solution is decanted, which is then a solu-
tion of copper. The precipitate is to be well
PARTING. 221
washed, and may be melted into an ingot. It is
called parted silver. When this silver has been ob-
tained from a mass which had been refined by lead,
and when it has been well washed from the solution
of copper, it is very pure. Or the silver may be
separated from the nitric acid by adding to it mu-
riatic acid, with which it forms muriate of silver.
Muriate of silver may be decomposed by mixing it
with soda, and exposing it to a sufficient heat in a
crucible, whereby the soda unites to the muriatic
acid, and sets the silver free.
The refiners frequently employ this solution of
copper obtained in the process of parting, for
making verditer ; which is prepared by adding
quick lime to the solution ; a precipitate takes
place, which is the blue pigment known by the
name of verditer.
Parting gold from silver by cementatio7i. — This
is also called parting by concentration, and is
usually employed when the quantity of gold is so
great to that of the silver, as to render it a difficult
task by aqua fortis. The mixed metal to be
cemented is to be reduced to plates, as thin as
small pieces of money. At the bottom of the cru-
cible, or melting-pot, is to be laid a stratum of
cement, composed of four parts of bricks powdered
and sifted, one part of green copperas (sulphate of
iron) calcined to redness, and one part of common
salt, about the thickness of a finger in depth. Upon
this stratum a layer of plates of the metal is to be
placed, and then another stratum of cement, and
so on till the crucible is filled. It is now to be
placed in a furnace, or oven (after a top has been
luted on the crucible,) and exposed for twenty-
four hours, till it is gradually made red hot, but
by no means to be melted. The fire is now left to
2f22 REFINING MFTALS.
go out, and the metal is permitted to cool, that it
may be separated from the cement, and boiled re-
peatedly in large quantities of pure water. This
gold is afterwards to be tried on a touch-stone ;
and if it is not sufficiently purified, the process
must be performed a second time. By the abov^e
method, we see how powerfully silver is dissolved
by muriatic acid, when it is in a state of subtile va-
pour which is disengaged from the common salt
of the cement. Instead of common salt, nitre may
be used, as the nitrous acid readily dissolves silver ;
but the mixture of common salt and nitre together
is highly injudicious, because the joint acids are
able to dissolve some of the gold with the silver.
Whatever silver has been separated, will now re-
main in the cement ; but it may be freed from this
by lead, in the method described in cupellation.
Parting gold from silver in the dry *way, — This is
also called jjarting by fusion^ and is performed by
means of sulphur, which has the property of uniting
easily with silver, while it does not attack gold.
This dry parting is troublesome, and even expen-
sive, and ought not to be undertaken but when the
silver far exceeds the gold, because sulphur will
not separate it so easily as aqua fortis, and will
therefore require a further application to cupell-
ation and solution.
Refining Silver by Nitre.
The principle upon which this operation is
founded, consists in the property of nitre to oxy-
date very powerfully all base metals; whereas, on
the contrary, the noble metals are not at all affected
by it. For as the metallic oxides and glasses do
REFINING METALS. 20,3
not remain united with reguline metals, and as
these latter sink to the bottom when in fusion, on
account of their greater specific gravity, they may
be easily parted from the scoriae.
The silver to be purified by nitre is to be first
granulated, and then mixed with a fourth part of its
weight of dry nitre, an eighth part of potash, and
a little common glass, all in powder. This mixture
is to be put into a good crucible, two-thirds of
which only must be full. This crucible is to be
covered with a smaller crucible inverted, in the
bottom of which a small hole has been made, and
luted to the former. The crucibles, thus disposed,
are to be placed in a furnace capable of drawing
air sufficiently to make the fire intense enough only
to melt the silver. Then charcoal is to be put into
the furnace to such a height, that only the top of
the inverted crucible shall be uncovered. The coal
is then to be kindled, and the vessels to be made
moderately red ; a hot coal ought to be put upon
the small hole in the bottom of the inverted cruci-
ble. If a shining light be observed round this
coal, and a slight hissing noise at the same time
heard, we may know that the operation proceeds
well. The fire must be sustained at the same
degree till these appearances cease, when it must
be increased, so that the silver be well melted, and
then the crucibles are to be taken out of the fur-
nace. The larger crucible is to be broken when it
is cold, and the silver will be found at the bottom
covered with green alcaline scoriae. If the metal
be not sufficiently ductile, the operation must be
again repeated.
Some silver is apt to be lost in this operation, by
the swelling and detonation of the nitre, which
often forces it through the hole in the upper cru-
224 REFINING METALS.
cible, unless great care be used ; nevertheless, this
method has its advantages, being much more expe-
ditious than cupellation.
Separating Silver from Copper by Eliquation.
When it is desired to separate, in the large way,
a small quantity of silver from much copper with
which it is alloyed, the process called eliquation is
resorted to. This operation is grounded on the
nearer affinity of silver with lead than with copper ;
in consequence of which it fuses, and combines with
lead at a degree of heat in which copper continues
imfused.
Whitening Silver hy Boiling.
Whitening of silver by boiling is one of the me-
thods of parting copper from silver in the humid
way. For this purpose, silver wrought in any
shape is first ignitei.1 to redness, and afterwards
boiled in a ley of muriate of soda, and acidulous
tartrite of potash. By so doing, the copper is re-
moved from the surface, and the silver receives a
better appearance.
Precipitating Silver by Copper.
Copper has a much greater affinity v/ith oxygen
than silver ; consequently, the silver is precipitated
from its solutions as a fine silver dust, by metallic
copper. This likewise affords a means to discover
what portion of silver may be contained in an alloy
of silver and copper. A quantity of the mixture
determined by weight is dissolved in nitric acid j
REFINING METALS. 225
the solution is diluted with water, filtered, and a
plate of copper hung in it, till no more precipitate
falls down. Then the weight of the precipitate,
when edulcorated, is compared v/ith that of the
whole alloyed metal put to trial.
This silver dust well washed, and mixed with
gum water, serves as a pigment in water painting.
Separating Silver from Copper hy an Alcaline
Sulphuret.
The affinity of copper with sulphur is stronger
than that of silver. Upon this ground, liver of
sulphur (sulphuret of potash) has been proposed as
an expedient to free silver from copper ; for if
silver holding copper be fused with alcaline sul-
phuret, the base metal combines with the latter,
and is converted into scoriae floating on the silver,
Mr. Keir*s Mode of separating Silver from Copper*
Chemists have long been acquainted with the
compound acid, called aqiia regia (nitro-muriatic
acid), which has the exclusive property of dissolv-
ing gold. The discovery of a compound acid, act-
ing exclusively upon silver, is owing to Mr. Keir.
This compound acid is made by dissolving one
pound of nitrate of potash (common nitre or salt-
petre), in eight or ten pounds of sulphuric acid (oil
of vitriol), or by mixing together sulphuric and
nitric acids. This acid dissolves silver easily,
while it will not attack copper, iron, lead, gold, or
platina.
These properties have rendered it capable of a
very useful application in the arts. Among the
manufactures at Birmingham, that of making ves-
VOL. II. Q
%%^ REFINING METALS.
sels of silver, plated on copper, is a very consider-
able one. On cutting out the rolled plated metal
into pieces of the required form and sizes, there
are many shreds, or scraps, as they are called, unfit
for any purpose, but the recovery of the metals, by
separating them from each other. The easiest and
most e'conomical method of parting these two me-
tals, so as not to lose either of them, is an object
of some consequence to the manufacturers. For
this purpose, two modes were practised ; one, by
melting the whole of the mixed metals with lead,
and separating them by eliquation and testing ; and
the second, by dissolving both metals in sulphuric
acid, with the help of heat, and by separating the
sulphate of copper, by dissolving it in water, from
the sulphate of silver, which is afterwards to be
reduced and purified.
In the first of these methods, there is a consi-
derable waste of lead and copper ; and in the se-
cond, the quantity of sulphuric acid employed is
very great, as much more is dissipated in the fonn
of sulphureous acid than remains in the composi-
tion of the two sulphates.
Some years ago, Mr. Keir communicated to an
artist the method of effecting the separating of
silver and copper, by means of the above-mentioned
compound of sulphuric acid and nitre. It is now
commonly practised by the manufacturers at Bir-
mingham, and is much more economical, and much
easier executed, that any of the above-mentioned
methods ; for nothing more is necessary than to
put the pieces of plated metal into a glazed earthen
pan, to pour upon them some of the acid liquor, to
stir them about, that the surfaces may be frequently
exposed to fresh liquor, and to assist the action by
a gentle heat, from 100« to 200'^ Fahr.
REFINING METALS. 2@7
When the liquor is nearly saturated, the silver is
to be precipitated from it by common salt, which
forms muriate of silver, or luna cornea, easily re-
ducible to a metallic state, by melting in a cru-
cible, with a sufficient quantity of potash ; and
lastly, by refining the melted silver, if necessary,
with a little nitre thrown upon it. In this manner,
the silver will be obtained sufficiently pure, and
the copper will remain unchanged. Otherwise,
the silver may be precipitated in its metaUic state,
by adding to the solution of silver a few of the
pieces of copper, and a sufficient quantity of water
to enable the liquor to act upon the copper.
Method of obtaining Gold in a pure State.
Perfectly pure gold may be obtained, by dis-
solving the gold of commerce in nitro muriatic
acid, and precipitating the metal, by adding a
weak solution of sulphate of iron. The precipitate,
after being well washed and dried, is pure gold.
Method of obtaining Silver in a pure State.
Dissolve the silver of commerce in nitric acid,
and add to it some muriatic acid ; a white curdy
precipitate will be formed, which is muriate of
silver. To reduce muriate of silver to the metallic
state, let one part of it be mixed with three of
soda, and exposed to a white heat. When the
mixture is well fused, suffer it to cool j then break
the crucible, and separate the pure silvei' from the
muriate of soda which has been formed.
Q 2
228 POTTERY.
Method of obtaiiiing pure Coppe?\
Let the copper of commerce be dissolved in mu-
riatic acid, and precipitate it by a polished plate of
iron ; the precipitate is pure copper.
Of making Brass, and other Alloys of Copper.
Brass is made by fusing together lapis calami-
naris (which is an ore of zinc) and copper.
Tombac is formed by melting together twelve
parts of copper with three of zinc.
Gun 7netal consists of nine parts of copper and
one of tin.
Bell metal is copper alloyed with one sixth of tin.
A smaller proportion of tin is used in making
church bells than clock bells, and a little zinc is
added for the bells of repeating-watches, and other
small bells.
Cock metal is made with copper alloyed with zinc
and lead.
The gold coins of this country are composed of
eleven parts of gold and one of copper.
Standard silver contains fifteen parts of silver
and one of copper.
POTTERY.
Pottery, or the art of making vessels of baked
earth, is of the remotest antiquity. The ancient
Greeks and Etruscans particularly excelled in it.
Porcelain, the most perfect of species of pottery,
has been made in China from time immemorial.
Alumine and silex are the two substances of which
every kind of earthen-ware is made. Clay alone
shrinks and cracks j the flint gives it solidity and
strength.
POTTERY. 229
Common Pottery, such as coarse brown jugs,
&c. are made of the ordinary clays, which are a
mixture of sand and chiy, coloured by oxide of
iron. The clay is well ground, or kneaded, and a
lump of it is put upon the centre of a wheel which
is kept in motion ; then, by means of the work-
man's liand, or by proper tools, it is formed into
the required shape. The pieces are then dried
moderately, so as to bear being removed without
danger ; they are then covered with a glaze, made
from semi-vitreous oxide of lead, and put into a
furnace, where they are baked. Some sorts are
glazed by throwing sea-salt into the furnace among
the different pieces of pottery. The salt is de-
composed, and the vapours of it form a glazing
upon the vessels ; but this, though a very simple
and ingenious method, does not form a good
glazing.
English stone-ware is made of tobacco pipe clay
mixed with flints calcined and ground. This ma-
nufacture owes its present state of perfection to
that enlightened manufacturer the late Mr. Wedge-
wood, who spared no pains or expense to improve
the art of pottery. He first introduced a superior
kind of which he called Queen's ware. The clay
of which it is made comes chiefly from the neigh-
bourhood of Corfe Castle in Dorsetshire. It
burns extremely white. The pipe clay is much
beat in water ; by this process tlie finer parts
remain suspended in the water, while the coarser,
sand, and other impurities, fall to the bottom.
The thick liquid, consisting of water and the finer
parts of the clay, is further purified by passing it
through hair and lawn sieves, of different degrees
of fineness. After this, the liquid is mixed (in
various proportions for various wares) with another
Q 3
2M) POTTERY*
li^nofr of the same density, and consisting of flints
calcined, ground, and suspended in water. The
mixture is then dried in a kiln ; and being after-
wards beaten to a proper temper, it becomes fit for
being formed at the wheel into dishes, plates,
bowls, &c. When this ware is to be put into the
furnace to be baked, the several pieces of it are
placed in cases made of clay, called seggars, which
are piled one upon another in the dome of the
furnace ; a fire is then lighted, and the ware is
brought to a proper temper for glazing, and in this
state it is called biscuit. Before the glazing takes
place it is coloured or painted, Formerly the
painting was done by the pencil by hand. It is
now commonly effected by taken impressions on
pdper from engraved copper plates, and transfer-
ring them to the earthenware while the ink is wet.
The ink is instantly absorbed by the biscuit, and
the paper is washed oif. The ink for the blue and
white ware is made from oxide of cobalt. It is
then dipped into a glaze, made by mixing together
in water, till it becomes as thick as cream, one
hundred and twelve parts of white-lead, twenty-
four parts of ground flint, and six parts of ground
flint-glass. The ware, by being bakedj acquires a
strong property of imbibing moisture, and when
dipped into the glaze, therefore, it greedily attracts
it into its pores, and presently becomes dry. It is
then exposed a second time to the fire, by which
means the glaze it has imbibed is melted, and a
thin glassy coat is formed upon its surface. The
colour of the coat is more or less yellow, according
as a greater or less proportion of lead has been
used. The lead is principally instrumental in pro-
ducing the glaze, as well as in giving it the yellow
colour} for lead, of all the substances hitherto
Lottery. 251
known, has the greatest power of promoting the
vitrification of the substances with which it is
mixed. TJie flint serves to give a consistency to
the lead during the time of its vitrification, and to
hinder it from becoming too fluid, and running
down the sides of the ware, and thereby leaving
them unglazed.
This glazing, made by means of lead, is liable to
be attacked by acids, and is supposed to be pro-
ductive of deleterious effects, when employed in
jars used for pickling, &c.
The following composition has been recom-
mended as a substitute.
To make this, white glass and soda, in equal
portions, must be very finely pulverized, carefully
sifted, and well mixed. The mixture is then ex-
posed to a strong heat, till it is rendered very dry.
It is afterwards put into vessels which have been
already bilked; it is then melted, and the varnish
is made. It may be applied in the same manner
as that m common use.
The advantage of it is, that it is safe, and can
have none of those poisonous effects which arise
from the decomposition of the lead varnish.
A variety of ware has been of late manufactured
which the potters call lustre. The glazing is
formed with platina, or gold. For the first, the
platina is dissolved in the nitro-muriatic acid with
heat: by adding muriate of ammonia, a yellow
precipitate falls down : wash and dry it, grind this
powder with a small portion of enamel, in oil of
turpentine, and spread it thinly over the glazed
surface of the earthen-ware. The ware is now
baked in a kiln with a red heat, and the platina
will assume the metallic brilliancy.
The gold is managed in the same way.
Q 4
23^ POTTERY-
The bla^k *ware owes its colour to the oxides of
of iron and manganese. It has also less flint, and
is more burned ; its compactness renders glazing
unnecessary.
Porcelaifi, called also CImia, from being first
brought from China, is the most beautiful and per-
fect species of earthen-ware.
Genuine or true porcelain, is a semi-vitrified
earthen-ware, intermediate between common ware
and glass. It is infusible in the strongest fire ex-
cited in furnaces ; it is hard, but not so brittle as
glass : it is proof against sudden changes of heat
and cold : it is fine grained, and dense without
gloss in the fracture, and is translucent. The
Chinese long excelled in the art of making porce-
lain, but it is now made in various parts of Europe
of an equally good quality and more ornamental.
The Chinese porcelain is said to be composed of
two ingredients, one of which is a hard stone called
pehmtse, which is carefully ground to a very fine
powder ; and the other, called kaoIi?i, is a white
earthy substance which is intimately mixed with
the ground stone.
Several compositions of mingled earths may
yield a true porcelain, by being burnt; and the
porcelain of various countries differ in their mix-
tures. But the principal basis of any true porce-
lain is that kind of clay M'hich becomes white by
baking, and which, either by intermingled hetero-
geneous earth, or by particular additions undergoes
in the fire an incipient vitrificatior,, in which the
true nature of porcelain consists. Feldspar and
gypsum, if added, may give that property to in-
fusible clay.
When porcelain is to be made, the clay is pro-
perly selected, carefully washed from impurities,
POTTERY. 233
and again dried. It is then finely sifted, and most
accurately mingled with quartz, ground very fine j
to which, then, is added some burnt and finely
pulverized gypsum. This mass is worked with
water to a paste, and duly kneaded ; it is usually
suffered to lie in this state for years. The vessels
and other goods formed of this mass, are first
moderately burnt in earthen pots, to receive a cer-
tain degree of compactness, and to be ready for
glazing. The glazing consists of an easily melted
mixture of some species of earths, as the petrosilex
or chert, fragments of porcelain and gypsum,
which, when fused together, produce a crystalline,
or vitreous mass, that, after cooling, is very finely
ground, and suspended in a sufficient quantity of
water. Into this fluid the rough ware is dipped,
by which the glazing matter is deposited uniformly
on every part of its surface. After drying, each
article is thoroughly baked or burned in the violent
heat of the porcelain furnace. It is usual to deco-
rate porcelain by paintings, for which purpose,
enamels or pastes, coloured by metallic oxydes,
are used, so easy of fusion as to run in a heat less
intense than that in which the glazing of the ware
melts.
Delft-warCf so called because first made at Delft
in Holland, is a kind of pottery made of sand and
clay, and but slightly baked, so that it resists sud-
den application of heat. Articles made of this are
glazed with an enamel, composed of common salt,
sand ground fine, oxyde of lead, and oxyde of tin.
The use of the latter is to give opacity to the
glaze.
Tobacco-pipes require a very fine tenacious, and
refractory clay, which is either naturally of a per-
fectly white colour, or, if it have somewhat of a grey
234 POTTERY.
cast will necessarily burn white. A clay of this
kind must contain no calcareous or ferruginous
earth, and must also be carefully deprived of any
sand it may contain, by washing. It ought to
possess, besides, the capital property of shrinking
but little in the fire. If it should not prove suffi-
ciently ductile, it may be meliorated by the ad-
mixture of another sort. Last of all, it is beaten,
kneaded, ground, washed, and sifted, till it
acquires the requisite degree of fineness and
ductility.
When, after this preparation, the clay has ob-
tained a due degree of ductility, it is rolled out in
small portions to the usual length of a pipe, per-
forated with a wire, and put together wdth the
wire, into a brass mould rubbed over with oil, to
give it its external form ; after wdiich it is fixed
into a vice, and the hollow part of the head formed
with a stopper. The pipes, thus brought into
form, are cleared of the redundant clay that adheres
to the seams, a rim or border is made round the
head, they are then miarked with an iron stamp
upon the heel, and the surfaces smoothed and
polished. When they are well dried, they are put
into boxes and baked in a furnace.
In the Dutch manufactories, these boxes consist
of conical pots made of clay, with conical lids, with
a tube passing through the middle of them, by which
the pipes are supported ; or else, they are long clay
boxes, in which the pipes are laid horizontally, and
stratified with fragments of pipes pounded small.
Lastly, the pipes, when baked, are covered with
a glazing or varnish, and afterwards rubbed with a
cloth. This glazing consists of a quarter of a
pound of soap, two ounces of white wax, and one
ounce of gum arabic, or tragacanth, which are all
I
I
MANUFACTURE OF GLASS. ^35
boiled together in five pints of water, for the space
of a few minutes.
MANUFACTURE OF GLASS.
This beautiful material is not of modern inven-
tion ; it was known to the ancient Romans, but it
was by no means common among them, and they
do not appear to have had the method of forming
it into vessels of various shapes as is practised at
present.
Glass is made by fusing together silex and
potash^ or soda, in proper proportions. Sea sand^
which consists almost entirely of quartz arid flints
reduced to powder, is generally used for this pur-
pose. The alcali is generally procured from the
burning of sea weeds ; these are cut, dried, and
burned in pits dug in the ground ; after a sufficient
quantity of them have burned in the same pit, a
melted or liquid mass is found in the bottom,
which, after being well stirred, is suffered to cool ;
it is then called kelp, and consists of a mixture of
soda, potash, and parts of half burnt v/eeds, toge-
ther with shells, sand, and other impurities.
When the ingredients of which glass is composed
are perfectly fused, and have acquired a certain
degree of heat, which is known by the fluidity of
the mass, part of the melted matter is taken out at
the end of a long hollov/ tube, which is dipped
into it, and turned about, till a sufficient quantity
is taken up ; the workmen then rolls it gently
upon a piece of iron, to unite it more intimately.
He then blows through the tube, till the melted
mass at the extremity swells into a bubble, after
236 MANUFACTURE OP GLASS.
which he rolls it again on a smooth surface to
polish it, and repeats the blowing, until the glass
is brought as near the size and form of the vessel
required as he thinks necessary.
If it be a common bottle, the melted glass at the
end of the tube is put into a mould of the exact
size and shape of its body, and the neck is formed
on the outside, by drawing out the ductile glass.
If it be a vessel with a wide orifice, the glass in
its melted state is opened and widened with an
iron tool ; after which being again heated, it is
whirled about with a circular motion, and by means
of the centrifugal force thus produced, is extended
to the size required. Should a handle, foot, or
any thing else of the kind, be required, these are
made separately, and stuck on in its melted state.
WindoxiD'glass is made in a similar manner, ex-
cept that the liquid mass at the end of the tube is
formed into a cylindrical shape, which being cut
longitudinally by scissars or sheers, is gradually
bent back until it becomes a flat plate.
Large plate glass, for looking-glasses, S^x, is
made by suffering the mass in a state of complete
fusion to flow upon a table, with iron ledges to
confine the melted matter, and as it cools, a metal-
lic roller is passed over it, to reduce it to an uniform
thickness. There are various kinds of glass manu-
factured for different purposes ; the principal of
these are flint-glass, crown-glass, and bottle-glass.
Flint-glass is the densest, most transparent,
colourless, and beautiful. It is sometimes called
crystal. The best kind is said to be manufactured
in London, from 120 parts of white siliceous sand,
40 parts of pearl-ash, 35 of red oxyde of lead, IS
of nitrate of potash, and 25 of black oxyde of man-
ganese. It is the most fusible glass. It is used
MANUFACTURE OF GLASS. 237
for bottles, and other utensils, intended to be cut
and polished, and for various ornamental purposes.
Crown-glass differs from the last, in containing
no lead. It is made of soda and fine sand. It is
used for panes of windows, &c.
Bottle-glass is the coarsest sort of all. It is
made from kelp and common sand. Its green
colour is owing to iron. It is the least fusible.
Glass is sometimes coloured by mixing with it
while in a fluid state, various metallic oxyds. It
is coloured blue, by the oxyd of cobalt ; red, by
the oxyd of gold ; green, by the oxyd of copper
or iron ; yellow, by the oxyd of silver or anti-
mony, and violet, by the oxyd of manganese.
The hardness of glass is very considerable ; its
specific gravity varies from 2. 3 to 4, according to
the quantity of metallic oxyd which enters into
its composition. Though glass, when cold, is
brittle, it is one of the most ductile bodies known.
When liquid, if a thread of melted glass be drawn
out, and fastened to a reel, the whole of the glass
can be spun off; and by cutting the threads of a
certain length, there is obtained a sort of feather of
glass. A thread of glass may be thus drawn or
spun so fine, as to be scarcely visible to the naked
eye. Glass is almost perfectly elastic, and is one
of the most sonorous bodies. Fluoric acid dis-
solves it at common temperatures, and alcalis in a
great degree of heat. These are the only sub-
stances known wiiich act upon it.
Glass utensils require to be gradually cooled
in an oven: this operation is called annealing, and
is necessary to prevent their breaking by change
of temperature, wiping, or slight accidental
scratches.
238 MANUFACTURE OF GLA3S.
Two toys are made of imannealed glass, which,
though commonly used for the amusement of chil-
dren, exhibit phenomena which justly interest the
curiosity of the philosopher; we mean Prince
Rupert's drops, and the Bologna flask or philoso-
phical phial.
Prince Riiperfs Drops are made by letting drops
of melted glass fall into cold water : the drop as-
sumes, by that means, an oval form, with a tail or
neck resembling a retort. These drops are said to
have been first invented by Prince Rupert, and
are, therefore, called by his name. They possess
this singular property, that if a small portion of the
tail is broken off, the whole bursts into powder with
an explosion; and a considerable shock is commu-
nicated to the hand that grasps it.
The Bologna or philosophical phial, is a small
vessel of glass, which has been suddenly cooled,
open at the upper end, and rounded at the bottom.
It is made so thick at the bottom, that it will bear
a smart blow against a hard body, without break-
ing ; but if a little pebble, or piece of flint, is let
fall into it, it immediately cracks, and the bottom
falls into pieces : but unless the pebble or flint is
large and angular enough to scratch the surface of
the glass, it will not break.
The most generally received explanation of these
facts is founded on the assumption, that the dimen-
sions of those bodies which are suddenly cooled,
are larger than those which are more gradually
cooled. The dimensions, therefore, of the smooth
external surface of these glasses which are suddenly
cooled, are supposed to be larger than is adapted to
the accurate envelopement of the internal part,
which is necessarily cooled in a more gradual man-
VARNISHING. 239
ner ; if, therefore, by a crack or scratch, a disjunc-
tion of the cohesion takes place, in the internal sur-
face, the hidden action of the parts which remained
in a state of tension, to recover that of perfect co-
hesion, is supposed to effect the destruction of the
the mass.
VARNISHING.
By varnish is understood a clear limpid fluid,
capable of hardening, without losing its transpa-
rency ; used by painters, gilders, &c. to give a
lustre to their works, and to preserve and defend
them from the air and moisture.
A coat of varnish ought to possess the following
properties: 1. It must exclude the action of the
air : because wood and metals are varnished to de-
fend them from decay and rust. 2. It must resist
water j for otherwise the effect of the varnish could
not be permanent. 3. It ought not to alter such
colours as are intended to be preserved by this
means. It is necessary, therefore, that a varnish
should be easily extended or spread over the sur-
face, without leaving pores or cavities, that it should
not crack or scale, and that it should resist water.
. Resins are the only bodies that possess these pro-
perties, consequently they must form the basis of
every varnish. For this purpose they must be dis-
solved, as minutely divided as possible, and com-
bined in such a manner, that the imperfections of
those that might be disposed to scale, may be cor-
rected by others.
Resins may be dissolved by three agents: 1. by
fixed or fat oil; 2. by volatile, or essential oil;
3. by spirit of wine. Accordingly, we have three
kinds of varnish : fat^ or oily varnish ; essential oil
varnish ; and spirit varnish.
240 VARNISHING.
These agents are of such a nature as either to
dry up and become hard, or to evaporate and fly
off, leaving the resin fixed behind.
Varnishes should be carefully kept from dust,
and in very clean vessels: they should be laid as
thin and even as possible with a large flat brush,
taking care to lay the strokes all one way. A warm
room is best for varnishing in, as cold chills the
varnish, and prevents it from laying even.
Varnishes are jiolisJied with pumice-stone and
tripoli. The pumice-stone must be reduced to a
very fine powder, and put upon a piece of serge
moistened v»'ith vv^ater; witli this the varnished sub-
stance is to be rubbed equally and lightly. The
tripoli must also be reduced to a fine powder, and
put upon a clean woollen cloth, moistened with
olive-oil, with which the polishing is to be per-
formed. The varnish is then to be wiped with soft
linen, and, when quite dry, cleaned M'ith starch, or
Spanish- white, and rubbed with the palm of the
hand, or with a linen cloth.
Fat Oil Varnish.
Fixed or fat oil will not evaporate ; nor wifl it
become dry of itself. To make it dry, it must be
boiled with metallic calces or oxides. Litharge is
generally used for this purpose. Oil so prepared is
called drying-oil. To accelerate the drying of oil
varnish, oil of turpentine is added.
Gum-copal, and amber, are the substances prin-
cipally employed in oil varnishes ; the copal being
whitest, is used for varnishing light, the amber for
dark colours.
It is best to dissolve them before mixing them
with the oil j because, by this means, they are in
VARNISHING. §41
less danger of being scorched, and at the same time
the varnish is more beautiful. They should be
melted in an iron pot over the fire : they are in a
proper state for receiving the oil when they give
no resistance to the iron spatula, and when they
run off from it drop by drop.
To make oil varnish, pour lour, six, or eight
ounces of drying-oil among sixteen ounces of
melted copal, or amber, by little and little, con-
stantly stirring tlie ingredients at the same time,
with the spatula. When the oil is well mixed with
the copal or amber, take it off the fire ; and when
it is pretty cool, pour in sixteen ounces of the
essence of Venice turpentine. After the varnish
is made, it should be passed through a linen cloth.
Oil varnishes become thick by keeping; but
when they are to be used, it is only necessary to
pour in a little Venice turpentine, and to put them
a little on the fire. Less turpentine is necessary in
summer than in the winter : too much oil hinders
the varnish from drying; but when too little is
used, it cracks, and does not spread properly.
Black Varnish for Coaches and Iron- Work.
This varnish is composed of asphaltum, resin,
and amber, melted separately, and afterwards
mixed; the oil is then added, and afterwards the
turpentine, as directed above. The usual propor-
tions are, twelve ounces of amber, two of resin, two
of asphaltum, six of oil, and twelve of turpentine.
A Varnish for rendering Silk Water and Air-ttghl.
To render the linseed-oil drying, boil it with
two ounces of sugar of lead, and three ounces of
VOL. II. R
^42 VARNISHING. ,
litharge, for every pint of oil, till the oil has dis-
solved them; then put a pound of bird-lime, and
half a pint of the drying oil into a pot of iron or
copper, holding about a gallon; and let it boil
gently over a slow charcoal lire, till the bird-lime
ceases to crackle; then pour upon it two pints and
a half of drying-oil, and boil it for about an hour
longer, stirring it often with an iron or wooden
spatula. As the varnish in boiling swells much, the
pot should be removed from the fire, and replaced
when the varnish subsides. While it is boiling, it
should be occasionally examined, in order to deter-
mine whether it has boiled enough. For this pur-
pose, take some of it upon the blade of a large
knife, and after rubbing the blade of another knife
upon it, separate the knives; and when, on their
separation, the varnish begins to form threads be-
tween the two knives, it has boiled enough, and
should be removed from the fire. When it is almost
cold, add about an equal quantity of spirits of tur-
pentine; mix both well together, and let the mass
rest till the next day; then having warmed it a
little, strain and bottle it. If it is too thick, add
spirits of turpentine. This varnish should be laid
upon the stuff when perfectly dry, in a lukewarm
state; a thin coat of it upon one side, and, about
twelve hours after, two other coats should be laid
on, one on each side ; and in twenty-four hours the
silk may be used.
Mr. Blcmchard's Var7iishfor Air-balloons.
Dissolve elastic gum (Indian-rubber), cut small,
in five times its'*weight of spirits of turpentine, by
keeping them some days together ; then boil one
ounce of this solution in eight ounces of drying
VARNISHING. g4S
linseed-oil for a few minutes, and strain it. Use
it warm.
Essential Oil Varnish,
The essential varnishes consist of a solution of
resin in oil of turpentine. This varnish being ap-
plied, the turpentine evaporates, leaving the resin
behind. They are commonly used for pictures.
To dissolve Gum Copal in Oil of Turpentine.
AVhatever quantity is to be dissolved should be
put into a glass vessel capable of containing at
least four times as much, and it should be high in
proportion to its breadth.
Reduce two ounces of copal to small pieces, and
put them into a proper vessel. Mix a pint of oil
of turpentine with one-eighth part of spirit of sal
ammoniac; shake them well together, put them to
the copal; cork the glass, and tie it over with a
string or wire, making a small hole through the
cork. Set the glass in a sand heat, so regulated as
to make the contents boil as quickly as possible,
but so gently, that the bubbles may be counted as
they rise from the bottom. The same heat must be
kept up exactly till the solution is complete.
It requires the most accurate attention to suc-
ceed in this operation. After the spirits are mixed,
they should be put to the copal, and the necessary
degree of heat be given as soon as possible. It
should likewise be kept up with the utmost regu-
larity. If the heat abates, or if the spirits boil
quicker than is directed, the solution will immedi-
ately stop, and it will afterwards be iu vain to pro-
ceed with the same materials; but if properly
R 2
S44 VARNISHING.
managed, the spirit of sal ammoniac will be seen
gradually to descend from the mixture, and attack
the copal, which swells and dissolves, except a very
small quantity which remains undissolved.'
It is of much consequence tliat the vessel should
not be opened till some time after it has been per-
fectly cold. It has happened, on uncorking the
vessel, when it v/as not warm enough to affect the
hand, that the whole of the contents were blown
with violence against the ceiling. It is likewise
important, that the spirit of turpentine should be
of the best quality. The turpentine bought at the
colour-shops seldom answers ; it should be had
from Apothecaries' hall.
This varnish is of a rich deep colour, when
viewed in the bottle, but seems to give no colour
to the pictures it is laid on. If left in the damp,
it remains tacky, as it is called, a long time ; but
if kept in a warm room, or placed in the sun, it
dries as well as any other turpentine varnish ; and
when dry, it appears to be as durable as any other
solution of copal.
Spirit Varnishes,
When resins are dissolved in alkohol, com-
monly called spirits of wine, the varnish dries very
speedily, but is subject to crack. This fault is
corrected by adding a small quantity of oil of tur-
pentine, which renders it brighter, and less brittle
when dry.
To dissolve Gum Copal in Spirits of Wine.
Dissolve half an ounce of camphor in a pint of
alkohol, or spirits of wine ', put it into a circulat-
VARNISHING. 245
ing glass, and add four ounces of copal, in small
pieces ; set it in a sand-heat so regulated, that the
bubbles may be counted as they rise from the bot-
tom ; and continue the same heat till the solution
is completed.
Camphor acts more powerfully upon copal than
any other substance. If copal is finely powdered,
and a small quantity of dry camphor rubbed with
it in the mortar, the whole becomes in a few
minutes a tough coherent mass. The process
above described will dissolve more copal than the
menstruum will retain when cold. The most
economical method will, therefore, be,\to set the
vessel which contains the solution by for a few
days ; and when it is perfectly settled, pour off
the clear varnish, and leave the residuum for a
future operation.
This is a very bright solution of copal : it is an
excellent varnish for pictures, and may, perhaps,
be found to be an improvement in fine japan
works, as the stoves used in drying those articles
,may drive ofi'the camphor entirely, and leave the
copal pure and colourless upon the work.
N. B. Copal will dissolve in spirit of turpentine,
by the addition of camphor, with the same facility,
but not in the same quantity, as in alkohol.
A Varnish for Wainscot, Cane Chairs, ^c.
Dissolve in a quart of spirits of wine, eight
ounces of gum sandarach, two ounces of seed-lac,
and four ounces of resin ; then add six ounces of
Venice turpentine. If the varnish is to produce
a red colour, more of the lac and less of sandarach
should be used, and a little dragon's blood should
be added. This varnish is very strong.
R 3
S^ VARNISHING.
A Variiishfor Toilet-Bocces, Cases, Fans, 8^c.
Dissolve two ounces of gum mastich, and eight
ounces of gum sandarach, in a quart of alkohol j
then add four ounces of Venice turpentine.
A Varnish for Violins^ and other Musical
Instruments.
Put four ounces of gum sandarach, two ounces
of lac, two ounces of gum m>astich, an ounce of
gum elemi, into a quart of alkohol, and hang them
over a slow fire till they are dissolved ; then add
two ounces of turpentine.
Varnish for employing Vermilion for painting
Equipages.
Dissolve in a quart of alkohol six ounces of
sandarach, three ounces of gum lac, and four
ounces of resin ; afterwards add six ounces of the
cheapest kind of turpentine : mix it with a pro-
per quantity of vermilion when it is to be used.
Seed-lac Varnish.
Take spirits of wine, one quart j put it in a
wide mouthed bottle, add thereto eight ounces of
seed-lac, that is large grained, briglit, and clear,
free from dirt and sticks ; let it stand two days, or
longer, in a warm place, often shaking it. Strain
it through a flannel into another bottle, and it is
fit for use.
VARNISHING. 24,7
Shell-lac Varnish.
Take one quart of spirits of wine, eight ounces
of the thinnest and most transparent shell-lac,
which, if melted in the flame of a candle, will
draw out in the longest and finest hair ; mix and
shake these together, and let them stand in a
warm place for two days, and it is ready for use.
This varnish is softer than that which is made
from seed-lac, and, therefore, is not so useful ; but
may be mixed with it for varnishing wood, &c.
White Varnish for Clock Faces, ^c.
Take of spirits of wine, highly rectified, one
pint, which divide into four parts ; then mix one
part with half an ounce of gum mastich, in a phial
by itself J one part of spirits, and half an ounce
of gum sandarach, in another phial ; one part of
spirits, and half an ounce of the whitest parts of
gum-benjamin. Then mix and temper them to
your mind. It would not be amiss to add a little
bit of white resin, or clear Venice turpentine, in
the mastich bottle ; it will assist in giving a gloss.
If your varnish prove too strong and thick, add
spirits of wine only ; if too hard, some dissolved
mastich ; if too soft, some sandarach or benjamin.
No other rule can be given, unless the quality of
the gums and the spirits could be ascertained.
When you have brought it to a proper temper,
warm the silvered plate before the fire, (if a clock
face, taking care not to melt the wax,) and with
a flat camel's-hair pencil, stroke it all over imtil
no white streaks appear. This will preserve silver-
ing many years.
R 4
^^' 248
JAPANNING.
Japanning is properly the art of varnishing and
painting ornaments on wood, in the same manner
as is done by the natives of Japan in the East
Indies.
The substances which admit of being japanned
are ahnost all kinds that are dry and rigid, or
not too flexible ; as wood, metals, leather, and
paper prepared.
Wood and metals do not require any other pre-
paration but to have their surfaces perfectly even
and clean ; but leather should be securely strained,
either on frames or on boards ; as its bending, or
forming folds, would otherwise crack and force off
the coats of varnish. Paper should be treated in
the same manner, and have a previous strong coat
of some kind of size ; but it is rarely made the
subject of japanning till it is converted into papier
mache, or wrought by other means into such form,
that its original state, particularly with respect to
flexibility, is changed.
One principal variation from the method for-
merly used in japanning is, the omitting any prim-
ing, or undercoat, on the work to be japanned.
In the older practice, such a priming was always
employed ; the use of it was to economize the
varnish by filling up the inequalities in the surface.
But there is a gieat inconvenience arising- from
the use of it, that the japan coats are constantly
liable to be cracked and peeled off by any vio-
lence, and will not last near so long as the articles
which are japanned without any such priming.
The French still retain the use of this under-
coat, and their japanned goods are upon that
JAPANNING. 249
account less durable than those manufactured at
Birmingham, where it is not used.
Of the Nature of Japan Grounds.
When a priming is used, the work should first
be prepared by being well smoothed with fish-skin
or glass-paper, and being made thoroughly clean,
should be brushed over once or twice with hot
size, diluted with two-thirds water, if it is of the
common strength. The priming should then be
laid on as even as possible, and should be formed
of a size, of a consistency between the common
kind and glue, mixed with as much whiting as
will give it a sufficient body of colour to hide
the surface of whatever it is laid upon, but
not more. This must be repeated till the inequal-
ities are completely filled up, and then the work
must be cleaned off with Dutch rushes, and
polished with a wet rag.
When wood or leather is to be japanned, and no
priming is used, the best preparation is to lay two
or three coats of coarse varnish, composed in the
following manner.
Take of rectified spirits of wine one pint, and of
coarse seed-lac and resin, each two ounces ; dis-
solve the seed-lac and resin in the spirit, and then
strain off the varnish.
This varnish, as well as all others formed of
spirit of wine, must be laid on in a warm place ;
and if it can be conveniently managed, the piece
of work to be varnished should be made warm like-
wise ; and for the same reason, all dampness should
be avoided ; for either cold or moisture chills this
kind of varnish, and prevents its taking proper
hold of the substance on v/hich it is laid.
250 JAPANNING.
When the work is so prepared, or by the priming
with the composition of size and whiting above
described, the proper japan ground must be
laid on, which is much the best formed of shell-
lac varnish, and the colour desired, except white,
which requires a peculiar treatment ; and if bright-
ness be wanted, then also other means must be
pursued.
The colours used with the shell-lac varnish may
be any pigments Mdiatever which give the tint of
the ground desired.
As metals never require to be imder-coated
with whiting, they may be treated in the same
manner as wood or leather.
White Japan Grounds,
The difficulty of forming a ground that shall be
at the same time hard and white, arises from there
being no substance that will form a very hard var-
nish, and yet have no colour. The best is made as
follows : Mix flake white, or white lead, with one-
sixth of its v/eight of starch, and dry the mixture,
and temper it v;ith mastich varnish. Lay this on the
substance to be japanned, with or without the under
coat of whiting; then varnish it with five or six
coats of a varnish made by dissolving two ounces
of picked lac, and three ounces of gum animi, in a
a quart of spirit of wine, straining off the clear
varnish.
A very good varnish, free from all brittleness,
may be formed, by dissolving as much gum animi
as the oil will take, in old nut, or poppy oil, boiled
gently, when the gum is put into it. The ground
of white colour may be laid on in this varnish, and
then a coat or two may be put over the ground :
JAPANNING. 251
but it must be well diluted with oil of turpentine
when it is used.
Blue Japan Grounds.
Blue japan grounds may be formed of bright
Prussian-blue; or of verditer, glazed over by Prus-
sian-blue, or smalt. The colour may be best mixed
with shell-lac varnish, and brought to a polishing
state by five or six coats of varnish of seed-lac; but
the varnish, nevertheless, will somewhat injure the
colour, by giving to a true blue a cast of green, and
fouling in some degree a warm blue by the yellow
it contains; where, therefore, a bright blue is, re-
quired, and a less degree of hardness can be dis-
pensed with, the method before directed in the
case of white grounds must be pursued.
Red Japan Grounds.
For a scarlet japan ground, vermilion may be
used; but the vermilion has a glaring effect, that
renders it much less beautiful than the crimson
produced by glazing it over with carmine or fine
lake, or even with rose pink, which has a very good
effect, used for this purpose. For a very bright
crimson, nevertheless, instead of glazing with car-
mine, the Indian lake should be used, dissolved in
the spirit of which the varnish is compounded,
which it readily admits of when good; and in this
case, instead of glazing with the shell-lac varnish,
the upper, or polishing coats need only be used, as
they will equally receive and convey the tinge of
the Indian lake, which may be actually dissolved
by spirits of wine, and this will be found a much
cheaper method than the using carmine. If^ liow-
ever, the highest degree of brightness is required,
the white varnish must be used.
S52 JAPANNING.
Yellow Japan Grounds.
For bright yellow grounds, king's yellow, or
turpeth mineral should be employed, either alone
or mixed with fine Dutch pink, and the effect may
be still more heightened, by dissolving powdered
turmeric root in the spirits of wine, of which the
upper or polishing coat is made; which spirits of
wine must be strained from off the dregs, before the
seed-lac be added to it, to form the varnish.
The seed-lac varnish is not equally injurious
here, and with greens, as is the case of other co-
lours; because, being only tinged with a reddish
yellow, it is little more than an addition to the force
of the colours.
Yellow grounds may be likewise formed of Dutch
pink only, which, when good, will not be wanting
in brightness, though extremely cheap.
Green Japan Grounds.
Green grounds may be produced by mixing
king's yellow and bright Prussian blue, or rather
turpeth-mineral and Prussian blue. And a cheap,
but fouler kind by verdigris, with a little of the
above mentioned yellows, or Dutch pink. But
where a very bright green is wanted, the crystals
of verdigris, called distilled verdigris, should be
employed; and to heighten the effect, they should
be laid on a ground of leaf gold, which renders the
colour extremely brilliant and pleasing.
Orange Japan Grounds,
Orange coloured japan grounds may be formed
by mixing vermilion, or red lead, with king's yel-
JAPANNING. 253
low, or Dutch pink, or the orange lake, which will
make a brighter orange ground than can be pro-
duced by any mixture.
Purple Japan Grounds.
These may be produced by the mixture of lake
and Prussian blue ; or of a darker kind, by Vermil-
lion and Prussian blue. They may be treated as
the rest, with respect to the varnish.
Black Japan Growids.
Black grounds may be formed without heat, by
either ivory black or lamp black ; but the former is
preferable where it is perfectly good. These may
always be laid on v;ith shell-lac varnish; and have
their upper, or polishing coats of common seed-
lac varnish, as the tinge or foulness of the varnish
can here be no injury.
Common black Japan grounds on iron or copper,
produced by means of heat, are formed thus : the
piece of work to be japanned must be painted over
with drying oil, and a little lamp black ; and when
it is of a moderate dryness, must be exposed to
such a degree of heat, as will change the oil to
black, without burning so as to destroy or weaken
its tenacity. The stove should not be too hot
when tire work is put into it, nor the heat increased
too fast, either of which errors would make it
blister ; but the slower the heat is augmented, and
the longer it is continued, provided it be restrained
within the due degree, the harder will be the coat
of japan. This kind of varnish requires no polish,
having received, when properly managed, a suffi-
cient one from the heat.
254 JAPANNING.
Tortoise-shell Japan Ground.
The best kind is made by means of a varnish
prepared in the following manner :
Take of good linseed-oil one gallon, and of umber
half a pound ; boil them together till the oil become
very brown and thick; strain it through a coarse
cloth, and boil it in till it acquire the consistence
of pitch.
Clean well the metal, or other pieces which are
to be japanned, and lay vermilion tempered with
shell-lac varnish, or with drying-oil diluted with
oil of turpentine, very thinly, on the places intended
to imitate the more transparent parts of the tortoise-
shelL When the vermilion is dry, brush over the
whole with the black varnish, tempered to a true
consistence with oil of turpentine; and when it is
set and firm, put the work into a stove, where it
may undergo a very strong heat, which must be
continued a considerable time ; if even three weeks
or a month it will be the better.
This was given amongst other receipts by
Kunckel ; but appears to have been neglected till
it was revived with great success in the Birming-
ham manufactures, where it was much used.
Method of painting Japan Work.
Japan w^ork ought properly to be pamted with
colours in varnish; though, for the greater dis-
patch, and in some very nice work in small, for the
freer use of the pencil, the colours are sometimes
tempered in oil ; which should previously have a
fourth part of its weight of gum animi dissolved in
it; or in default of that, gum sandarach, or gum
mastich. When the oil is thus used, it should be
JAPANNING. 255
well diluted with oil of turpentine, that the colours
may lay more evenly and thin ; by which means,
fewer of the polishing or upper coats of varnish be-
come necessary.
In some instances, water colours are laid on
grounds of gold, in the manner of other paintings;
and are best without any varnish over them. When
they are to have the effect of embossed work, the
colours for painting are prepared by means of isin-
glass size, with some honey or sugar candy. The
body of which the embossed woric is raised, need not,
however, be tinged with the exterior colour, but may
be formed of very strong gum water, thickened to
a proper consistence by bole armoniac and whiting
in equal parts; which being laid on the proper
figure and repaired when dry, may be then painted
with the proper colours, tempered with the isin-
glass size, or, in the usual manner, with shell-lac
varnish.
Manner of varnishing Japan I Fork,
The finishing of japan-work consists in laying on,
and polishing, tiie outer coats of varnish. This is in
general done best with common seed-lac varnish.
But where brightness is the most material point, and
a tinge of yellow will injure it, seed-lac must give
way to the whiter gums ; where hardness, and a
greater tenacity are most essential, it must be re-
tained; and the mixed varnish mentioned above,
under white japanned ground, made of the picked
seed-lac, must be adopted.
With respect to making this varnish, it may be
observed, that when the spirit of wine is very
strong, it will dissolve a greater proportion of the
seed-lac; but this quantity Vv'ill saturate the com-
mon, which is seldom of a strength sufficient to
2.56 JAPANNING.
make varnishes in perfection. As the chilling,
which is the most inconvenient accident attending
varnishes of this kind, is prevented, or produced
more frequently, according to the strength of the
spirit ; we shall show a method by which weaker
rectified spirits may be rendered of the first degree
of strength.
Take a pint of the common rectified spirit of
wine, and put it into a bottle, of which it vrill not
fill above three parts ; add to it half an ounce of
pearl-ashes, salt of tartar, or any other alcaline
salt, heated red hot, and powdered as well as it
can be vrithout much loss of its heat. Shake the
mixture frequently for the space of half an hour ;
before which time, a great part of the phlegm v/ill
be separated from the spirit, and will appear, toge-
ther with the undissolved part of the salts, in the
bottom of the bottle. Let the spirit be poured off
or freed from the phlegm and the salts, by means
of a separating funnel -, and let half an ounce of
the pearl-ashes, heated and powdered as before, be
added to it, and the same treatment repeated.
This may be done a third time, if the quantity of
phlegm separated by the addition of the pearl-
ashes appear considerable. An ounce of alum
reduced to powder, and made hot, but not burnt,
must then be put into the spirit, and sufiered to
remain some hours, the bottle being frequently
shaken ; after which the spirit being poured ofii*
from it, v/ill be fit for use.
The addition of the alum is necessary to neu-
tralize the remains of the alcaline salt, which
would otherwise greatly deprave the spirit.
The manner of using the seed-lac, or white
varnish, is the same, except with regard to the
substance used in polishing ; v.hich, where a pure
JAPAN.VIXG. 257
\\hite of a great clearness of other colours is in
question, should be itself white ; whereas the
browner sorts of polishing-dust, as being cheaper,
and doing their business with greater dispatch,
may be used in otlier cases. The pieces of work
to be varnished should be placed near a fire, or in
a room w here there is a stove, and made perfectly
dry ; and then the varnish may be rubbed over
them by the proper brushes made for that pur-
pose, beginning in the middle, and passing the
brush to one end, and then with another stroke
from the middle, passing it to the other. But
no part should be crossed, or twice passed over,
in forming one coat, where it can be possibly
avoided. When one coat is dry, another must be
laid over it ; ^nd this must be continued at least
five or six times, or more, if, on trial, there be not
sufficient thickness of varnish to bear the polish,
without laying bare the painting or ground colour
underneath.
When a sufficient number of coats is thus laid
on, the work is fit to be polished ; which must be
done, in common cases, by rubbing it w^th a rag,
dipped in tripoli, or rotten-stone, finely powdered ;
but, towards the end of the rubbing, a little oil of
any kind should be used along with the powder ;
and when the v/ork appears sufficiently bright and
glossy, it should be well rubbed with the oil alone,
to clean it from the powder, and give it a still
brighter lustre.
In case of white grounds, instead of tripoli, or
rotten-stone, fine putty, or whiting must be used ;
both of which should be washed over, to prevent
the danger of damaging the work, from any sand
or gritty matter that may happen to be mixed
with them.
VOL, lu s
2.5S LACQUERING.
It is a great improvement in all kinds ofjapanned
work, to harden the varnish by means of heat ;
which in every degree that it can be appUed, short
oi' what would burn or calcine the matter, tends
to give it a more firm and strong texture.
Where metal forms the body, a very hot stove
may be used ; and the pieces of work may be con-
tinued in it a considerable time, especially if the
heat be gradually increased ; but where wood is in
question, heat must be sparingly used, as it would
otherwise warp or shrink the body, so as to injure
the general figure.
LACQUERING.
Lacquering is the laying either coloured or
transparent varnishes on metals, in order to pro-
duce the appearance of a different colour in the
metal, or to preserve it from rust, or the injuries
of the weather.
Lacquering is used where brass is to be made
to have the appearance of being gilt ; where tin is
wanted to have the resemblance of yellow metals ;
and where brass locks or nails, or other such mat-
ters, are to be defended from the corrosion of the
air or moisture.
The principal substance used for the compo-
sition of lacquers, is seed-lac ; but for coarser pur-
poses, resin or turpentine is added, in order to
make the lacquer cheaper.
A Lacquer for Brass^ to imitate Gilding.
Take of turmeric one ounce, and of saffron and
Spanish annotto, each two drachms. Put them
9
LACQUERING. 259
into a proper bottle, with a pint of highly rectified
spirits of wine, and place them in a moderate heat,
often shaking them for several days. A very
strong yellow tincture will then be obtained,
which must be strained off from the dregs through
a coarse linen cloth ; and then, being put back
into the bottle, three ounces of good seed-lac,
powdered grossly, must be added, and the mixture
placed again in a moderate heat and shaken till
the seed-lac be dissolved, or at least such a part of
it as may. The lacquer must then be strained, and
must be put into a bottle well corked.
Where it is desired to have the lacquer warmer
or redder than this composition, the proportion of
the annotto must be increased ; and wdiere it is
wanted cooler, or nearer to a true yellow, it must
be diminished.
The above, properly managed, is an extremely
good lacquer, and of moderate price ; but the
following, which is cheaper, and may be made
where the Spanish annotto cannot be procured
good, is not greatly inferior to it.
Take of turmeric root, ground, one ounce, of
the best dragon's blood half a drachm. Put them
to a pint of spirits of wine, and proceed as above.
By diminishing the proportion of dragon's blood,
the varnish may be rendered of a redder or truer
yellow cast.
Saffron is sometimes used to form the body of
colour in this kind of lacquer, instead of the tur-
meric ; but though it makes a warmer yellow, yet
the dearness of it, and the advantage which tur-
meric has in forming a much stronger tinge in
spirits of wine, gives it the preference. Though
being a true yellow, and consequently not suffi-
ciently warm to overcome the greenish cast of
s 2
mo
LACQUERIXG.
brass, it requires the addition of some orange
coloured tinge to make it a perfect lacquer.
Aloes and gamboge are also sometimes used in
lacquers for brass ; but the aloes is not necessary
where turmeric or saffron is used ; and the gam-
boge, though a very strong milky juice in water,
affords but a very weak tinge in spirit of wine.
A Lacquer for Tiny to imitate a Yellow Metal.
Take of turmeric root one ounce, of dragon's
blood two drachms, and of spirits of wine one
pint J add a sufficient quantity of seed-lac.
A Lacquer for Locks, S^-c.
Seed-lac varnish alone, or with a little dragon's
blood : or a compound varnish of equal parts of
seed-lac and resin, with or without the dragon's
blood.
A Gold-coloured Lacquer for gilding Leather.
What is called gilt leather, and used for screens,
borders for rooms, &c. is only leather covered
with silver leaf, and lacquered with the following
composition.
Take of fine white resin four pounds and a half,
of common resin the same quantity, of gum san-
darach two pounds and a halfj and of aloes two
pounds ; mix them together, after having bruised
those which are in great pieces, and put them into
an earthen pot, over a good fire made of charcoal,
or over any fire where there is no flame. Melt all
GILDING. Q6l
the ingredients in this manner, stirring them well
witli a spatula, that tliey may be thoroughly mixed
together, and be prevented also from sticking to
the bottom of the pot. When they are perfectly
melted and mixed, and gradually to them seven
pints of linseed oil, and stir the whole well
together with the spatula. Make the whole boil,
stirring it all the time to prevent a kind of sediment
that will form, from sticking to the bottom of the
vessel. When the varnish is almost sufficiently
boiled, add gradually half an ounce of litharge, or
half an ounce of red-lead, and vhen they are dis-
solved, pass the varnish through a linen cloth, or
flannel bag.
The time of boiling this varnish should be about
seven or eight hours. This, however, varies, ac-
cording to circumstances. The way of knowing
when it is sufficiently boiled, is by taking a little on
some instrument, and if it draws out and is ropy,
and sticks to the fingers, drying on them, it is
done ; but if not, it must be boiled till it acquires
these qualities.
GILDING.
Gilding is the application of gold to the surfaces
of bodies: it is of two principal kinds, according
to the method of applying the gold. i
Wood, leather, paper, and similar substances,
are gilt by fastening on leaves of gold by means of
some cement. But metals are gilt by a chemical
application of the gold to the surface. This last
is called icater gilding.
The gilding of wood, and similar substances, is
of three kinds ; oil gilding, burnished gilding, and
Japamiers* gilding, y^hichwe shall severally describe,
s 3
'26^2 GILDING.
after noticing the materials and tools necessary for
going to work.
OfGold-Leaf.
There are three kinds of gold-leaf in common
use.
Pure gold'lecif, which is made by hammering
gold between the leaves of a book made of skins,
till they are sufficiently thin.
Pale leaf-gold, which has a greenish colour, and
is made of gold alloyed with silver.
Dutch gold, which is brought from Holland, and
is in fact only copper-leaf coloured by the fumes of
zinc. It is much cheaper than true leaf-gold, and
is very useful where large quantities of gilding are
wanted, which can be defended from the weather,
and where great nicety is not required ; but it
changes its colour entirely when exposed to mois-
ture ; and, indeed, in all cases, its beauty is soon
impaired, unless well secured by varnish. It is
therefore only a cheap substitute for true gold-leaf,
which may be useful where durability is not an
object.
Of the IfLStruments necessary Jbr Gilding.
The first instrument is the cushion, for receiving
the leaves of gold from the books in which they
are bought. It is made by covering a board of
about eight inches square, with a double thickness
of flannel, and over that, a piece of buff leather,
and fastening it tight round the edges.
The hiife for cutting the leaves into the requisite
sizes should be made like a pallet knife, and should
not have its edge too sharp.
GILDING.
•263
The tip is a tool made by fastening the long
hairs of a squirrel's tail between two cards, and is
used for taking up the gold-leaf after it is cut, and
applying it to the article to be gilded.
A^fitch pencil is used for the same purpose as the
last, in taking up very small bits of gold-leaf. A
ball of cotton is necessary for pressing down the
leaf, after it is laid on. A large cameVs-hair brush
is used lor dusting the work, and clearing away
the superfluous gold.
Oil Gildings
Prime the work with boiled linseed-oil and
white-lead ; and when that is dry, do it over with a
thin coat of gold size, made of stone ochre ground
in fat oil. When that is so dry as to feel clammy
to the fingers, or to be, as the gilders call it, tacky ^
it is fit for gilding. Having spread your leaves
upon the cushion, cut them into slips of the proper
width for covering the work. Then breathe upon
your tip, which, by moistening it, will cause it to
take up the leaves from the cushion. Plaving ap-
applied them by the tip on the proper parts of the
work, press them down by the ball of cotton.
Observe to repair, by putting small pieces of gold
on any parts which you have omitted to cover.
When all the work is sufficiently covered, let it
dry, and clean it off with the brush.
This sort of gilding is the easiest, least expen-
sive, and stands the weather best, and may be
cleaned with a little water at any time ; but wants
the lustre of burnished gilding.
s 4
-04 GILDING.
Burnished Gilding.
This is the sort of gilding generally used for
picture-frames, looking-glasses, &c.
The wood intended to be gilt in this manner
should first be well sized, and then done over with
seven or eight coats of size and whiting, so as to
cover it with a body of considerable thickness.
Having got a sufficient quantity of whiting upon
the work, it must be carefully cleaned off, taking
care to free all the cavities and hollows from the
whiting that may have choked them up, and by
proper moulds and tools restoring the sharpness
of the mouldings intended to be shown.
It is then to receive a coat of size, whicli is
made by boiling armeniac bole with parchment
size. This must also remain till it is sufficiently
dry for the gold. It must not be quite dry ; there-
fore it would not be prudent to lay on more at a
time, than can be gilt before it becomes too dry.
The work being thus prepared, place it a little
declining from you, and having a cup of clean
water ready and some hair pencils, moisten a part
of the work, and then apply the gold by the tip to
the moistened part. The gold will immediately
adhere close to the work : proceed to wet the next
part, and apply the gold as before, repeating this
operation till the whole is completed ; taking care
not to let any drops of water come upon any part
of the gold already laid on. Care should therefore
be taken, that no part be missed in going over it
at first, as it is not so easily mended as the oil
gilding.
The work being thus gilt, it is suffered to remain
about twenty-four hours j when the parts that are
GILDING. ^2(j5
designed to be burnished are polished with a dog's
tooth, or, wliat is better, with an agate burnisher.
The gilding must not be quite dry when it is bur-
nished; there is a state proper for the purpose,
which is only to be known by experience.
Japanners^ Gilding,
The gilding of japanned work consists in draw-
ing with a hair pencil, in gold size, the intended
ornaments, and afterwards applying gold leaf or
gold powder.
The gold size may be prepared in the following-
manner: take of linseed-oil, and of gum animi,
four ounces. Set the oil to boil in a proper vessel,
and then add the gum animi gradually in powder,
stirring each quantity about in the oil, till it appear
to be dissolved, and then putting in another, till
the whole be mixed with the oil. Let the mixture
continue to boil, till, on taking a small quantity
out, it appear of a thicker consistence than tar, and
then strain the whole through a coarse cloth, and
keep it for use ; but it must, when applied, be
mixed with vermilion and oil of turpentine.
Having laid on the gold size, and suffered it to
dry, the gold leaf is applied in the usual way, or if
it is not wanted to shine so much, gold powder is
applied, which is made by grinding gold leaf upon
a stone with honey, and afterwards washing the
honey away with water. If the gilding is to be
varnished over, Dutch gold may be used, or aurum
musivum may be used instead of real gold powder.
266 GILDING.
To write on Paper mth Letters of Gold.
Put some gum arabic into common wiiting ink,
and write with it in the usual way. When tlie
writing is dry, breathe on it ; the warmth and
moisture softens the gum, and will cause it to
fasten on the gold leaf, w^hich may be laid on in
the usual way, and the superfluous ])art brushed
off. Or instead of this,, any japanners' size may be
used.
To lay Gold upon White Earthen-Ware, or Glass.
Procure some japanners' gold size, and with it
draw your design upon the vessel to be gilt, moist-
ening the gold size, as you find necessary, with oil
of turpentine. Set your work in a clean place to
dry, for about an hour, and then place it so near
the fire that you could but just bear the heat of it
with your hand for a few seconds. Let it remain
there till it feels quite tacky or clammy, then,
having procured a cushion, and some leaf gold, cut
it into slips of the proper size, and lay it on with a
little cotton wool. When the gold is all on, put
the ware into an oven to be baked for two or three
hours.
Glasses, &c. may also be gilt by drawing the
figures with shell gold mixed with gum arabic and
a little borax. Then apply sufficient heat to it ;
and, lastly, burnish it.
Gilding on Glass or Porcelain, by Burning-in.
'Dissolve gold in aqua regia, and evaporate the
acid by heat ; a gold powder will be obtained ; or
GILDING. ^7
precipitate the gold from the solution by pieces of
copper. Lay this gold on with a strong solution
of borax and gum water, and it will be ready for
burning-in.
Gilding Metals.
One method of applying gold upon metals is by
first cleaning the metal to be gilt ; then gold leaf
is laid on it, which, by means of rubbing with a
polished blood stone, and a certain degree of heat,
are made to adhere. In this manner silver leaf is
fixed and burnished upon brass, in the making of
what is cdWed French plate ; and sometimes also
gold leaf is burnished upon copper and iron.
Gilding hy Amalgamation is by previously
forming the gold into a paste, or amalgam, with
mercury.
In order to obtain an amalgam of gold and
mercury, the gold is lirst to be reduced into thin
plates or grains, which are heated red-hot, and
thrown into mercury previously heated, till it be-
gins to smoke. Upon stirring the mercury with
an iron rod, the gold totally disappears. The pro-
portion of mercury to gold is generally as six or
eight to one.
The method of gilding by amalgamation is
chiefly used for gilding copper, or an alloy of cop-
per with a small portion of zinc, which more
readily receives the amalgam, and is also prefer-
able, on account of its colour, which more resem-
bles that of gold than the colour of copper.
When the metal to be gilt is wrought or chased,
it ought to be previously covered with quick-silver
before the amalgam is applied, that this may be
'268 GILDING.
easier spread ; but when the siirtace of the metal
is plain, the amalgam may be directly applied to it.
The metal required to be gilt is first rubbed over
with a little aqua-fortis, by which the surface is
cleaned from any rust or tarnish that might pre-
vent the union of the two metals. The amalgam,
being then equally spread over the surface by
means of a brush, the mercury is evaporated by a
heat just sufficient for that purpose; lor if it be
too great, part of the gold may also be expelled,
and part of it will run together, and leave some of
the surface of the metal bare. While the mercury
is evaporating, the piece is to be from time to time
taken from the fire, that it may be examined ; that
the amalgam may be spread more equally by
means of a brush ; that any defective parts of it
may be again covered, and that the heat may not
be too suddenly applied to it. When the mercury
is evaporated, which is known by the surface be-
coming entirely of a dull yellow colour, the metal
must then undergo other operations, by which the
fine gold colour is given to it.
First, the gilded piece of metal is rubbed with
a scratch-brush (which is a brush composed of
brass-wire,) till its surface is made smooth ; tlien it
is covered over with a composition called gilding
'waxj and is again exposed to the fire till the wax
be burnt off. This wax is composed of bees-wax,
sometimes mixed with some of the following sub-
stances, red ochre, verdigris, copper scales, alum,
vitriol, borax ; but according to Dr. Lewis, the
saline substances are sufficient, without any wax.
By this operation the colour of the gilding is
heightened ; and this effect seems to be produced
by a perfect dissipation of some mercury remain-
ing after the former operation.
GILDING. 269
The gilt surface is tiien covered over with a
sahiie composition, consisting of nitre, alum, or
other vitriohc salt, ground together, and mixed
up into a paste with water or urine. The piece
of metal thus covered is exposed to a certain de-
gree of heat, and then quenched in water. By
this method its colour is further improved, and
brought nearer to that of gold. This effect seems
to be produced by the acid of nitre (which is dis-
engaged by the sulphuric acid of the ahim, during
the exposure to heat) acting upon any particles of
copper which may happen to lie upon the gilded
surface.
Lastly, some artists tliink that they give an ad-
ditional lustre to their gilt work, by dipping it in
a liquor prepared by boiling some yellow materials,
as sulphur, orpiment, or turmeric. The only ad-
vantage of this operation is, that part of the yel-
low matter remains in some of the hollows of the
carved work, in which the gilding is apt to be
more imperfect, and to w^iich it gives a rich and
solid appearance.
It may here be noticed, that the use of the aqua-
fortis or nitrous acid, mentioned in the beginning
of the process, is not, as is generally supposed,
confined merely to cleansing the surface of the
metal to be gilt from rust or tarnish j but it also
greatly facilitates the application of the amalgam
to the surface of that metal, probably in the fol-
lowing manner : It first dissolves part of the mer-
cury of the amalgam ; and when this solution is
applied to the copper, this latter metal having a
stronger disposition to unite with the nitrous acid
than the mercury has, precipitates the mercury
upon its surface, in the same manner as a polished
piece of iron precipitates upon its surface copper
270 GILDING.
from a solution of blue vitriol. When the metal
to be gilt is thus covered over with a thin coat
of precipitated mercury, it readily receives the
amalgam.
On the subject of gilding by amalgamation, Dr.
Lewis has the following remarks : " There are
two principal inconveniencies in this business ;
one, that the workmen are exposed to the fumes of
the mercury, and generally, sooner or later, have
their health greatly impaired by them : the other,
the loss of the mercury ; for though part of it is
said to be detained in the cavities made in the
chimneys for that purpose, yet the greatest part of
it is lost. From some trials I have made, it ap-
peared that both these inconveniencies, particu-
larly the first and most considerable one, might be
in a good measure avoided, by means of a furnace
of a due construction."
If the communication of a furnace with its chim-
ney, instead of being over the fire, is made under
the grate, the ash-pit door, or other apertures be-
neath the grate, closed, and the mouth of the fur-
nace left open, the current of air, which otherwise
would have entered beneath, enters now at the top,
and passing down through the grate to the chim-
ney, carries with it completely both the vapour of
the fuel, and tlie fumes of such matters as are
placed upon it. The back part of the furnace
should be raised a little higher above the fire than
the fore part, and an iron plate laid over it, that
the air may enter only at the front where the
workman stands, who will be thus effectually se-
cured from the fumes, and from being incom-
moded by the heat, and at the same time have full
liberty of introducing, inspecting, and removing
the work.
GILDTNG, Oyi
If such a furnace is made of strong forged (not
milled) iron plate, it will be sufficiently durable.
The upper end of the chimney may reach above a
foot and a half higher than the level of the fire ;
over this is to be placed a larger tube, leaving an
interval of an inch, or more, all round between it
and the chimney, and reaching to the height of ten
or twelve feet ; the higher the better. The exter-
nal air, passing up between the chimney and the
outer pipe, prevents the latter from being much
heated, so that the mercurial fumes will condense
against its sides into running quicksilver, which
falling down to the bottom, is there catched in a
hollow rim, formed by turning inwards a portion
of the lower part, and conveyed by a pipe at one
side into a proper receiver.
Gilding Iron or Steel, — In gilding iron or steel
by means of an amalgam, as the metal has no
affinity for the mercury, an agent must be em-
ployed to dispose the surface to receive the gilding.
For this purpose, a solution of mercury in nitrous
acid (aqua fortis,) or what the workmen call quick-
silver water, is applied to the parts intended to
be gilded ; the acid, by a stronger affinity, seizes
on a portion of the iron, and deposits in the place
of it a thin coating of mercury, which will not
refuse a union afterwards with the gold amalgam
that may be applied ; but, by this process, the
surface of the metal is injured by the nitrous acid,
and the union of the mercury is very slight, so
that a bright and durable gilding cannot be
obtained.
Another method. — Sometimes a solution of blue
vitriol is applied, with a cameFs hair pencil, to the
parts of the steel intended to be gilt. By a che-
mical action, exactly similar to what we have
f27!2 filLDIXG.
described as taking place wlien a solution of nitrate
of mercury is employed, a thin coating of copper
is precipitated on the metal. Copper having an
affinity for mercury, a kind of union may by this
means be effected between the amalgam and the
iron or steel, as the case may be. In whichever
of these ways the amalgam be brought into imion
with the steel, the surface is injured by the action
of the acid employed, and still a heat sufficient to
volatilize the mercury, must be afterwards used.
Gilding of Iron by heat. — When the surface is
polished bright, it must be heated till it becomes
blue. Gold leaf is then applied to its surface, and
burnished down. It is then heated again, and
another layer of gold burnished on it. In this
manner three or four coats are given, according to
the strength of the gilding intended. This is a
more laborious process than the two last, but it is
not attended with so much risk.
An improved process for gilding Iron or Steel. —
This process, which is less known among artists
than it deserves to be, may prove useful to those
who have occasion to gild iron or steel. The
first part of the process consists in pouring over a
solution of gold in nitro-muriatic acid (aqua regia)
about twice as much ether, which must be done
with caution, and in a large vessel. These liquids
must then be shaken together ; as soon as the
mixture is at rest, the ether will be seen to separate
itself from the nitro-muriatic acid, and to float on
the surface. The nitro-muriatic acid becomes
more transparent, and the ether darker than they
were before ; the reason of which is, that the
ether has taken the gold from the acid. The whole
mixture is then to be poured into a glass funnel,
the lower aperture of which is small j but this
GILDING. 273
aperture must not be opened till the fluids have
compleely separated themselves from each other.
It is then to be opened ; by which means the
liquid which has taken the lowest place by its
greater gravity, viz. the nitro-muriatic acid will
run off; after which, the aperture is to be shut,
and tha funnel will then be found to contain
nothing but ether mixed with the gold, which is
to be put into well-closed bottles, and preserved
for use. In order to gild iron or steel, the metal
must first be well polished with the finest emery,
or rather with the finest crocus martis, or colcothar
of vitriol, and common brandy. The auriferous
ether is then to be applied with a small brush ; the
ether soon evaporates, and the gold remains on the
surface of the metal. The metal may then be put
into the fire, and afterwards polished. By means
of this auriferous ether, all kinds of figures may
be delineated on iron, by employing a pen, or fine
brush. It is in this manner, probably, that the
Sohlinger sabre blades are gilded.
Instead of ether, the essential oils may be used ;
such as oil of turpentine, or oil of lavender, which
will also take gold from its solution.
Cold Gilding of Silver. — Dissolve gold in the
nitro-muriatic acid, and dip some linen rags in t!.e
solution ; then burn them, and carefully preserve
the ashes, which will be very black, and heavier
than common. When any thing is to be gilded, it
must be previously well burnished ; a piece of
cork is then to be dipped, first into a solution of
salt in water, and afterwards into the black powder ;
and the piece, after being rubbed with it, must be
burnished. This powder is frequently used for
gilding delicate articles of silver.
VOL. II. T
274 GILDING.
Gilding of Brass or Copper. — Fine instruments
of brass, in order that their surface may be kept
longer clean, may be gilded in the following
manner.
Provide a saturated solution of gold, and having
evaporated it to the consistence of oil, suffer it to
shoot into crystals. These crystals must then be
dissolved in pure water, and the articles to be
gilded being immersed in it, are then to be washed
in pure water, and afterwards burnished. This
process may be repeated several times, till the arti-
cles have been well gilt. A solution of gold
crystals is preferred to a mere solution of gold j
because, in the latter, there is always a portion of
free acid, which will not fail to exercise more or
less action on the surface of the brass or copper,
and injure its polish.
Grecian Gilding. — Dissolve some mercury in
muriatic acid (spirits of salts), which will give a
muriate of mercury. Mix equal parts of this and
sal ammoniac, and dissolve them in aqua fortis.
Put some gold into this, and it will dissolve.
When this is applied to silver, it becomes black ;
but by heating, it assumes the appearance of
gilding.
To make Shell-Gold.
Grind up gold-leaf with honey, in a mortar ;
then wash away the honey with water, and mix
the gold-powder with gum-water. This may be
applied to any article with a camel's-hair pencil,
in the same way as any other coloui'.
5^75
SILVERING.
Wood, paper, &c. are silvered in the same
manner as gilding is performed, using only silver
instead of gold-leaf.
To Silver Copper or Brass.
Cleanse the metal with aqua fortis, by washing it
lightly, and then throwing it into the water ; or by
scouring it with salt and tartar with a wire-brush.
Dissolve some silver in aqua fortis, and put pieces
of copper into the solution ; this will throw down
the silver in a state of metallic powder. Take
fifteen or twenty grains of this silver powder, and
mix with it two drachms of tartar, the same quan-
tity of common salt, and half a drachm of alum ;
rub the articles with this composition till they are
perfectly white, then brush it off, and polish them
with leather.
Anotfier method. — Precipitate silver from its so-
lution in aqua fortis by copper, as before ; to half
an ounce of this silver add common salt and sal
ammoniac, of each two ounces, and one drachm
oi corrosive sublimate ; rub them together, and
make them into a paste with water. With this,
copper utensils of every kind, that have been pre-
viously boiled with tartar and alum, are rubbed ;
after which they are made red hot and polished.
To Silver the Dial-plates of Clocks^ Scales of Ba-
7^omete7'S, S^x.
Take half an ounce of silver lace, add thereto
an ounce of double refined aqua fortis ; put them
into an earthen pet, and place them over a gentle
T 2
276 SILVERING.
fire till all is dissolved, which will happen in about
five minutes ; then take them off, and mix it in a
pint of clear water; after which, pour it into another
clean vessel, to free it from grit or sediment ; then
add a spoonful of common salt, and the acid, which
has now a green tinge, will immediately let go the
silver particles, which form themselves into a white
curd; pour off the acid, and mix the curd with two
ounces of salt of tartar, half an ounce of whiting,
and a large spoonful of salt, more or less, accord-
ing as you find it for strength. Mix it well up to-
gether, and it is ready for use.
Having well cleared the brass from scratches,
rub it over with a piece of old hat and rotten-stone,
to clear it from all greasiness, and then rub it with
salt and water with your hand : take a little of the
before-mentioned composition on your finger, and
rub it over where the salt has touched, and it will
adhere to the brass and completely silver it. After
which, wash it well with water, to take ofi' what
aqua fortis may remain in the composition ; when
dry, rub it with clean rag, and give it one or two
coats of varnish, prepared according to the direc-
tions given under the article varnislies.
This silv^ering is not durable, but may be improved
by heating the article, and repeating the operation
till the covering seems sufficiently thick.
Silver Plating.
The coat of silver applied to the surface of the
copper by the means mentioned above, is very
thin, and is not durable. A more substantial
method of doing it, is as follows : form small pieces
of silver and copper, and tie them together with
SILVERING. 277
wire, putting a little borax between. The pro-
portion of silver may be to that of the copper as
one to twelve. Put them into a white heat, when
the silver will be firmly fixed to the copper. Th;s
whole is now made to pass between rollers, till it
is of the required thickness for manufacturing
various articles.
To make French Plate.
Heat the copper articles intended to be plated,
and burnish silver-leaf on it, with a burnisher.
To make Shell Silver.
Grind up leaf-silver with gum-water or honey ;
when you have ground it, wash away the gum or
honey, and use the powder that remains with gum-
water, or glaire of eggs. This is laid on with a
hair-pencil.
To silver Looking Glasses.
The following apparatus must first be prepared.
1. A square marble slab, or smooth stone, well
polished, and ground flat; the larger the better;
with a frame round it, or a groove cut in its edges,
to keep the superfluous mercury from running off.
2. Lead weights, covered with cloth, to keep
them from scratching the glass; from one pound
weight to twelve pounds each, according to the
size of the glass which is laid down.
3. Rolls of tinfoil.
4. Quicksilver.
Cut the tinfoil a little larger than the glass every
way, and lay it flat upon the stone; and with a
straight piece of hard wood, about three inches
T 3
278 SILVERING.
long, stroke it every way, that there be no crease
or wrinkles in it; then drop a little mercury upon it,
and with a piece of cotton, w^ool, or hair's foot,
spread it all over the foil, so that every part may
be touched with the mercur}-. Then, keeping the
marble slab nearly level with the horizon, pour the
mercury over the foil ; cover it with a fine paper ;
and lay two weights very near its lowest end or
side, to keep the glass steady, while you draw the
paper from between the silvered foil and the glass,
which must be laid upon the paper. As you draw
the paper, you must take care that no air bubbles
be left ; for they will always appear, if left in at the
first. You must likewise be sure to make the glass
as clean as possible on the side intended to be sil-
vered, and have the paper also quite clean ; other-
wise, when you have drawn the paper from under
it, dull white streaks will appear, which are very
disagreeable.
After the paper is drawn out, place as many
weights upon the glass as you conveniently can,
in order to press out the superfluous mercuiy, and
make the foil adhere to the glass. When it has
lain six or seven hours in this situation, raise the
stone about two or three inches at its highest end,
that as much of the mercury may run off as possi-
ble ; let it remain two days before you venture to
take it up» But before you take the weights offj
gently brush the edges of the glass, that no mer-
cury may adhere to them ; then take it up, and
turn it directly over, wuth its face side downward ;
but raise it by degrees, that the mercury may not
drip off too suddenly : for if, when taken up, it is
immediately set perpendicular, air will get in
between the foil and the glass at the top, as the
mercury descends to the bottom ; by which means.
SILVERING. 279
if you be not exceedingly careful, your labour will
be lost.
Another method, is to slide the glass over the
foil, without the assistance of paper.
To Silver Glass Globes,
Take half an ounce of clean lead, and melt it
with an equal weight of pure tin; then immediately
add half an ounce of bismuth, and carefully skim
off the dross J remove the mixture from the fire,
and, before it grows cold, add five ounces of mer-
cury, and stir the whole well together ; then put
the fluid amalgam into a clean glass, and it is fit
for use.
When this amalgam is used for foiling or silver-
ing, let it first be strained through a linen rag ;
then gently pour some ounces of it into the
globe intended to be foiled : the mixture should be
poured into the globe, by means of a glass or paper-
funnel, reaching almost to the bottom of the globe,
to prevent its splashing to the sides; the globe
should then be dexterously inclined every way,
though very slowly, in order to fasten the silver-
ing. When this is once done, let the globe rest
some hours ; repeat the operation, till at length the
fluid mass is spread even, and fixed over the whole
internal surface, as it may be known to be, by
viewing the globe against the light ; the super-
fluous amalgam may then be poured out, and the
outside of the globe cleared.
To Silver the Convex Side of Glasses for Mirrors.
Take an earthen plate, on which pour some pre-
pared plaster of Paris, mixed with water, of a
T 4
'2H0'
SILVERING*
proper consistence ; then immediately, before it
grows too stiff, lay the glass, with its convex
side downward, in the middle of the plate, and
press it until it lies quite close to the plaster ; in
which situation let it remain until the plaster be-
comes quite dry. After which, work a groove with
your fingei', round the outside of the glass, in
order to let the superfluous mercury rest upon it ;
then cut the tinfoil to a proper size, and press it
with the glass into the plaster-mould, in order
to make it lie close ; after which, cover it with the
mercury, and, without a paper (as directed for sil-
vering plain mirrors), slide it over the silvered foil ;
then place a weight on it, and let it stand two or
three days, rising it by degrees, that the mercury
may drip off gradually.
Afler this method common window-glass, &c.
may be silvered.
To la^ Paper Pi^ints on the Inside of Glass Globed,
First, cut off all the white part of your impres-
sion, so that nothing appear but the print ; then
prepare some strong gum arabic water, or size,
with which you must brush over the face side ;
after which put it into the globe, and with a long
small stick, on which a camel*s-hair pencil is fixed,
stick it even on ; and by this method you may put
what number of prints you please into the globe.
Let them dry about twelve hours; then pour some
prepared plaster of Paris, either white or tinged,
whatsoever colour you please, and turn the globe
easily about, so that every part be covered; pour
out the superfluous plaster, and it is finished.
28 1
TINNING.
Tinning is tlie art of covering any metal with a
tliin coating of tin. Copper and iron are the me-
tals most commonly tinned. The use of tinning
these metals is to prevent them from being cor-
roded by rust, as tin is not so easily acted upon by
the air or water as iron and copper are.
What are commonly called tin-plates, or sheets,
so much used for utensils of various kinds, are in
fact iron-plates coated with tin.
The principal circumstance in the art of tinning,
is to have tlie surfaces of the metal to be tinned
perfectly clean and free from rust, and also that
the melted tin be perfectly metallic, and not co-
vered with any ashes or calx of tin.
Tinning of Iron.
When iron-plates are to be tinned, they are first
scoured, and then put into what is called a pickle,
which is oil of vitriol diluted with water ; this dis-
solves the rust or oxyd that was left after scouring,
and renders the surface perfectly clean. They are
then again washed and scoured. They are now
dipped into a vessel full of melted tin, the surface
of which is covered with fat or oil, to defend it
from the action of the air. By this means, the iron
coming into contact with the melted tin in a
perfectly metallic state, it comes out completely
coated.
When a small quantity of iron only is to be
tinned, it is heated, and the tin rubbed on with
a piece of cloth, or some tow, having first sprinkled
the iron with some powdered resin, the use of which
is to reduce the tin that may be oxydated. Any
28'2 BRONZING.
inflammable substance, as oil, for instance, will have
in some degree, the same effect j which is owing to
their attraction for oxvffen.
^6'
The Tinning of Copper.
Sheets of copper may be tinned in the same man-
ner as iron. Copper boilers, saucepans, and other
kitchen utensils, are tinned after they are made.
They are first scoured ; then made hot ; and the tin
rubbed on, as before, with resin. Nothing ought to
be used for this purpose but pure grain-tin ; but
lead is frequently mixed with the tin, both to adul-
terate its quality, and make it lay on more easily;
but it is a very pernicious practice, and ought to be
severely reprobated.
To whiten Brass or Copper by boiling.
Put the brass or copper into a pipkin with some
white tartar, alum, and grain-tin, and boil them to-
fcether. The articles will soon become covered
with a coating of tin, which, when well polished,
will look like silver. It is in this manner that pins,
and many sorts of buttons, are whitened.
BRONZING.
Bronzing is colouring plaster, or other busts and
figures, with metallic powders, in order to make
them appear as if made of copper or other metals.
The powders used for this purpose are either fine
copper-filings, aurum musivum, or copper precipi-
tated from its solution in aqua fortis by iron. Having
done over the substance to be bronzed with a dark
green colour, the projecting parts are touched with
either isinglass size, japanners' gold size, or, in some
cases, with drying-oil, or oil-paint j the powders are
10
SOLDERING. 283
then rubbed on, taking care that the projecting
parts receive more of the powder than the cavities,
to imitate the brightness on those parts of bronze
which are Hable to be rubbed.
SOLDERING.
Soldering is the art of joining two pieces of me-
tal together, by heating them with a thin piece or
plate of metal interposed between them. Thus tin
is a solder for lead; brass, gold, or silver, are sol-
ders for iron, &c.
To make Silver Solder.
Melt fine silver two parts, brass one part ; do
not keep them long in fusion, lest the brass fly oft'
in fumes.
Ayiotlierfor coarser Silver.
Melt four parts of fine silver, and three of brass;
throw in a little borax, and pour it out as soon as it
is melted.
A Solder for Gold.
Melt copper one part, fine silver one part, and
gold two parts ; add a little borax when it is just
melted, then pour it out immediately.
The Method of soldering Gold or Silver.
After the solder is cast into an ingot, it would
be more ready for use if your were to draw it into
small wire, or flat it between two rollers ; after that
cut it into little bits ; then join your work together
with fine soft iron-wire ; and with a camel's-hair
per.cil, dipt in borax finely powdered and well mois-
tened with water, touch the joint intended to be
'iS'i MOULDING AND CASTING.
soldered; })lacing a little solder upon the joint,
apply it upon a large piece of charcoal, and, with a
blow-pipe and lamp, blow upon it the flame until it
melts the solder.
To cleanse Silver or Gold after it is soldered.
Make the silver red hot, and let it cool ; then
boil it in alum-water, in an earthen vessel, and it
will be as clean as when new. If gold, boil it in
urine and sal ammoniac.
A Solder for Lead,
Put two parts lead to one part tin: its goodness
is tried by melting it, and pouring the size of a
crown-piece upon the table ; if it be good, there
will arise little bright stars in it. Apply resin when
you use this solder.
A Solder for Tin.
Take four parts of pewter, one of tin, and one
of bismuth ; melt them together, and run them
into narrow thin lengths. >
A Solder for Iron.
Nothing here is necessary, but good tough brass,
with borax applied, mixed with water to the con-
sistence of paste.
MOULDING AND CASTING.
The art of taking casts or impressions from
pieces of sculpture, medals, &c. is of very great
importance in the line arts.
MOULDING AND CASTING.; 285
In order to procure a copy or cast from any
figure, bust, medal, &c. it is necessary to obtain a
mould by pressing upon the thing to be moulded
or copied, some substance which, when soft, is
capable of being forced into all the cavities or hol-
lows of the sculpture. When this mould is dry and
hard, some substance is poured into it, which will
fill all the cavities of the mould, and represent the
form of the original from which the mould was
taken.
The particular manner of moulding depends
upon the form of the subject to be worked upon.
When there are no projecting parts but such as
form a right or a greater angle with the principal
surface of the body, nothing more is required than
to cover it over with the substance of which the
mould is to be formed, taking care to press it well
into all the cavities of the original, and to take it
off clean, and without bending.
The substances used for moulding are various,
according to the nature and situation of the sculp-
ture. If it may be laid horizontally, and will bear to
be oiled without injury, plaster of Paris maybe advan-
tageously employed ; which may be poured over it
to a convenient thickness, after oiling it, to prevent
the plaster from sticking. A composition of bees-
wax, resin, and pitch, may also be usedj which will
be a very desirable mould, if many casts are to be
taken from it. But if the situation of the sculpture
be perpendicular, so that nothing can be poured
upon it, then clay, or some similar substance, must
be used. The best kind of clay for this purpose is
that used by the sculptors for making their models
with ; it must be worked to a due consistence, and
having spread it out to a size sufficient to cover all
the surface, it must be sprinkled over with whiting.
286 MOULDING AND CASTING.
to prevent it from adhering to the original. Bees-
wax and dough, or the crumb of new bread, may
also be used for moulding some small subjects.
When there are under cuttings in the bas relief,
they must be first filled up before it can be mould-
ed, otherwise the mould could not be got off. When
the casts are taken afterwards, these places must
be worked out with a proper tool.
When the model, or original subject, is of a round
form, or projects so much that it cannot be moulded
in this manner, the mould must be divided into
several parts j and it is frequently necessary to cast
several parts separately, and afterwards to join them
togetl^er. In this case, the plaster must be tem-
pered with water to such a consistence, that it may
be worked like soft paste, and must be laid on with
some convenient instrument, compressing it so as
to make it adapt itself to all parts of the surface.
When the model is so covered to a convenient thick-
ness, the whole must be left at rest till the plaster is
set and firm, so as to bear dividing without falling
to pieces, or being liable to be put out of its form
by any slight violence ; and it must then be divided
into pieces, in order to its being taken off from the
model, by cutting it with a knife with a very thin
blade ; and being divided, must be cautiously taken
off, and kept till dry: but it must be observed, be-
fore the separation of the parts be made, to notch
them across the joints, or lines of division, at pro-
per distances, that they may with ease and certainty
be properly put together again. The art of pro-
perly dividing the moulds, in order to make them
separate from the model, requires more dexterity
and skill than any other thing in the art of casting,
and does not admit of rules for the most advanta-
geous conduct of it in every case. Where the sub-
MOULDING AND CASTING. 287
ject is of a round or spheroidal form, it is best to
divide the mould into three parts, which will then
easily come off from the model ; and the same will
hold good of a cylinder, or any regular curve
figure.
The mould being thus formed and dry, and the
parts put together, it must be first oiled, and placed
in such a position that the hollow may lie upwards,
and then filled with plaster mixed with water; and
when the cast is perfectly set and dry, it must be
taken out of the mould, and repaired when neces-
sary, which finishes the operation.
In larger masses, where there would otherwise
be a great thickness of the plaster, a core may be
put within the mould, in order to produce a hollow
in the cast, which both saves the expense of the
plaster, and renders the cast lighter.
In the same manner, figures, busts, &c. may
be cast of lead, or any other metal in the moulds
of plaster or clay ; taking care, however, that the
moulds be perfectly dry ; for should there be any
moisture, the sudden heat of the metal would
convert it into vapour, which would produce an
explosion by its expansion, and blow the melted
metal about.
To take a Cast in Metal from any small Animaly
Insect, or Vegetable.
Prepare a box of four boards, sufficiently large
to hold the animal, in which it must be suspended
by a string ; and the legs, wings, &c. of the animal,
or the tendrils, leaves, &c. of the vegetable, must
be separated, and adjusted in their right position
by a pair of small pincers. A due quantity of
288 MOULDING AND CASTING.
plaster of Paris, mixed with talc, must be tempered
to the proper consistence with water, and the
sides of the box oiled. Also a straight piece of
stick must be put to the principal part of the
body, and pieces of wire to the extremities of the
other parts, in order that they may form, when
drawn out after the matter of the mould is set
and firm, proper channels for pouring in the metal,
and vents for the air ; which otherwise, by the
rarefaction it would undero;o from the heat of the
metals, would blow it out, or burst the mould.
In a short time the plaster will set, and become
hard j when the stick and wires may be drawn
out, and the frame or coffin in which the mould
was cast taken away ; and the mould must then be
put, first, into a moderate heat, and, afterwards,
when it is as dry as can be rendered by that de-
gree, removed into a greater, which may be gra-
dually increased, till the whole be red hot. The
animal or vegetable inclosed in the mould will
then be burnt to a coal ; and may be totally cal-
cined to ashes, by blowing for some time into the
charcoal and passages made for pouring in the
metal, and giving vent to the air, which will at
the same time that it destroys the remainder of
the animal or vegetable matter, blow out the ashes.
The mould must then be suffered to cool gently,
and will be perfect ; the destruction of the sub-
stance included in it having produced a corre-
sponding hollow ; but it may nevertheless be pro-
per to shake the mould, and turn it upside down,
as also to blow "vvith the bellows into each of the
air-vents, in order to free it wholly from any
remainder of the ashes j or, where there may be
an opportunity of filling the hollow with quick-
silver, it will be found a very effectual method of
MOULDING AND CASTING. S89
clearing tlie cavity, as all dust, ashes, or small
detached bodies, will necessarily rise to the surface
of the quicksilver, and be poured out with it.
The mould being thus prepared, it must be heated
very hot when used, if the cast is to be made
with copper or brass, but a less degree will serve
for lead or tin. The metal, being poured into the
mould, must be gently struck, and then suffered
to rest till it be cold ; at which time it must be
carefully taken from the cast, but without force ;
for such parts of the matter as appear to adhere
more strongly must be softened, by soaking in
water till they be entirely loosened, that none of
the more delicate parts of the cast may be broken
off or bent.
When talc cannot be obtained, plaster alone
may be used ; but it is apt to be calcined by the
heat used in burning the animal or vegetable from
whence the cast is taken, and to become of too
incoherent and friable a texture. Stourbridge,
or any other good clay, washed perfectly fine, and
mixed wdth an equal part of fine sand, may be
employed. Pounded pumice-stone, and plaster of
Paris, in equal quantities, mixed with washed clay
in the same proportion, is said to make excellent
moulds.
Method of taking a Cast in Plaster' from a
Fersoji's Face.
The person whose likeness is required in plaster
must lie on his back, and the hair must be tied
up so that none of it covers the face. Into
each nostril convey a conical piece of stiff paper
open at both ends, to allow of breathing. The
VOL. II. u
290 MOULDING AND CASTING.
face is then lightly oiled over in every part with
salad-oil, to prevent the plaster from sticking to
the skin. Procure some fresh burnt plaster, and
mix it with water to a proper consistence for
pouring. Then pour it by spoonfuls quickly all
over the face (taking care the eyes are shut), till
it is entirely covered to the thickness of a quarter
of an inch. This substance will grow sensibly
hot, and in a few minutes will be hard. This
being taken off will form a mould, in which a
head of clay may be moulded, and therein the
eyes may be opened, and such other additions
and corrections may be made as are necessary.
Then, this second face being anointed with oil,
a second mould of plaster must be made upon it,
consisting of two parts joined lengthwise along
the ridge of the nose ; and in this a cast in plas-
ter may be taken, which will be exactly like the
original.
To take Casts from Medals,
In order to take copies of medals, a mould must
first be made j this is generally either of plaster of
Paris, or of melted sulphur.
After having oiled the surface of the medal
with a little cotton, or a camePs hair pencil dip-
ped in oil of olives, put a hoop of paper round it,
standing up above the surface of the thickness you
wish the mould to be. Then take some plaster
of Paris, mix it with water to the consistence of
cream, and with a brush rub it over the surface of
the medal, to prevent air-holes from appearing;
then immediately afterwards make it to a sufficient
thickness, by pouring on more plaster. Let it
MOULDING AND CASTING. 291
stand about Iialf an hour, and it will in that time
grow so hard, that you may safely take it ofFj then
pare it smooth on the back and round the edges
neatly. It should be dried, if in cold or damp
weather, before a brisk fire. If you cover the
face of the mould with fine plaster, a coarser sort
will do for the back : but no more plaster should
be mixed up at one time than can be used, as it
will soon get hard, and cannot be softened without
burning over again.
Sulphur must not be poured upon silver medals,
as this will tarnish them.
To prepare this mould for casting sulphur or
plaster of Paris in, take half a pint of boiled lin-
seed oil, and oil of turpentine one ounce, and mix
them together in a bottle ; when wanted, pour
the mixture into a plate or saucer, and dip the
surface of the mould into it; take the mould out
again, and when it has sucked in the oil, dip it
again. Repeat this till the oil begins to stagnate
upon it ; then take a little cotton wool, hard rolled
up, to prevent the oil from sticking to it, and
wipe it carefully off. Lay it in a dry place for a,
day or two (if longer the better,) and the mould
will acquire a very hard surface from the effect of
the oil.
To cast plaster of Paris in this mould, proceed
with it in the same manner as above directed for
obtaining the mould itself, first oiling the mould
with olive oil. If sulphur casts are required, it
must be melted in an iron ladle.
Another viethod with Ishmlass. — Dissolve isin-
glass in water over the fire ; then, with a hair
pencil, lay the melted isinglass over the medal :
and when you have covered it properly, let it dry.
u 2
292 CEMENTS.
When it is hard, raise the isinglass up with the
point of a penknife, and it will fly off like horn,
having a sharp impression of the medal.
The isinglass may be made of any colour by mix-
ing the colour with it; or you may breathe on the
concave side, and lay gold leaf on it, which, by
shining through, will make it appear like a gold
medal. But if you wish to imitate a copper medal,
mix a little carmine with the isinglass, and lay gold
leaf on as before.
CEMENTS.
Cements require to be of various compositions,
according to the substances to which they are ap-
plied, and whether they are to be exposed to heat
and moisture.
Common Glue.
Common glue is formed by extracting by boil-
ing the gelatinous part of cuttings or scraps of
coarse leather, or the hides of beasts. It is then
poured out in thin cakes and dried.
Isinglass Glue.
Isinglass glue is made by dissolving beaten isin-
glass in water by boiling, and, having strained it
through a coarse linen cloth, evaporating it again,
o such a consistence, that being cold, the glue will
be perfectly hard and dry.
This cement is improved by dissolving the isin-
glass in any proof spirit by heat, or by adding to it
when dissolved in water, an equal quantity of spirits
of wine.
CEMENTS. 293
It is still further improved by adding to the
isinglass, previous to its solution in spirits, one-
third of its weight of gum ammoniac. Expose the
mixture to a boiling heat, until the isinglass and
gum are dissolved, and until a drop of the compo-
sition become stiff instantly as it cools. It will at
any future time melt with a degree of heat little
exceeding that of the human body, and, in conse-
quence of so soon becoming stiff on cooling, forms
a very valuable cement for many purposes, particu-
larly for the very nice and delicate one of fixing on
the antennae, legs, &c. of insects in cabinets of na-
tural history. The easy melting of this cement is
no objection to its use in cases where the articles
themselves may afterwards be exposed to moderate
heat ; for it owes this property only to the presence
of the spirit which evaporates soon after it has been
applied. When used to join broken glass or china,
the pieces to be joined should be previously warmed.
Immersion in hot water will give them a sufficient
degree of heat. Wipe off the water before applying
the cement, which may be laid on with a pencil ;
then press the pieces together, binding them with
a string, or bit of soft wire, if necessary.
This isinglass glue is far preferable to common
glue for nice purposes, being much stronger, and
less hable to be softened either by heat or moisture.
Parchment Glue.
Take one pound of shreds of parchment, or vel-
lum, and boil it in six quarts of water till the quan-
tity be reduced to one quart ; strain off the fluid
from the dregs, and then boil it again till it be of
the consistence of glue.
u 3
294 CEMENTS.
The same may be done with glovers* cuttings of
leather, which are dressed with alum instead of
being tanned ; this will make a colourless glue.
A good Glue for Sigii-BoardSy or any thing that
must sta?id the Weather.
Melt common glue with water to a proper con-
sistence ; then add one eighth of boiled linseed oil,
dropping it into the glue gently, and stirring it all
the time.
A very strong glue is made by adding some pow-
dered chalk to common glue.
Another that will resist water is made by adding
half a pound of common glue to two quarts of
skimmed milk.
Preparation of Lip Ghwyfor cementing Taper ^ Silk,
thin Leather, ^c.
Take of isinglass glue and parchment ghie, each
one ounce ; of sugar-candy, and gum tragacanth,
each two drachms ; add to them an ounce of water,
and boil the whole togetlier, till the mixture ap-
pears, when cold, of the proper consistence of glue.
Then form it into small roils, or any other figure
that may be most convenient.
This glue may be wet witli the tongue, and
rubbed on the edges of the paper, silk, &c. that are
to be cemented, which will, on their being laid to-
gether, and suffered to dry, unite as firmly as any
other part of the substance.
CEMENTS. '2D5
Lapland Glue.
The bows of the Laplanders are composed of
two pieces of wood glued together ; one of them
of birch, which is flexible, and the other of fir of
the marshes, which is stiff, in order that the bow
when bent may not break, and that when unbent
it may not bend. When these two pieces of wood
are bent, all the points of contact endeavour to
disunite themselves, and to prevent this, the Lap-
landers employ the following cement: they take
tlie skins of the largest perches*, and having dried
them, moisten them in cold water until they are so
soft tliat they may be freed from the scales, which
they throw away. They then put four or five of
these skins into a rein-deer*s bladder, or they wrap
them up in the soft bark of the birch-tree, in such
a manner that water cannot touch them, and place
them thus covered into a pot of boiling water, with
a stone above them to keep them at the bottom.
When they have boiled about an hour, they take
them from the bladder or bark, and they are then
found to be soft and viscous. In this state they
employ them for glueing together the two pieces of
their bows, which they strongly compress and tie
up till the glue is well dried. These pieces never
afterwards separate.
A Glue from Cheese.
Take skimmed-milk cheese, free it from the rind,
cut it into slices, and boil it in water, stirring it
* It is lU'obable that ecl-skius would answer the same purpose.
U 4
29Q CEMENTS.
Avitli a spoon until it be reduced to a strong glue,
"which does not incorporate with water. Then
throw away the hot water; pour cold water over the
glue, and knead it afterward in warm water, sub-
jecting it to the same process several times. Put
the warm glue on a grinding-stone, and knead it
with quick-lime until you have a good glue. When
you wish to use this glue you must warm it ; if it
be employed cold it is not so strong, but it may also
be used in that manner. This glue is insoluble in
water as soon as it is dry, and it becomes so in
forty-eight hours after it has been applied. It may
be used for glueing wood, and for cementing marble
and broken stone and earthen-ware. Baits for
catching fish may also be made of it. Fish are very
fond of it, and it resists water.
Jewellers' Cement
In setting precious stones, pieces are sometimes
broken off by accident. In such cases, they often
join the pieces so correctly, that an inexperienced
eye cannot discover the stone to have been broken.
They employ for this purpose a small piece of gum
mastich applied between the fragments, which are
previously heated sufficiently to enable them to
melt the interposed gum. They are then pressed
together, to force out the redimdant quantity of
gum.
Turkey Cement, Jbr jo hung Metals, Glass, ^c.
Dissolve five or six bits of mastich, as large as
peas, in as much spirits of wine as will suffice to
render it liquid ; in another vessel dissolve as much
CEMENTS. 297
isinglass (which has been previously soaked in
water till it is swollen and soft,) in brandy or rum,
as \vill make two ounces by measure of strong glue,
and add two small bits of gum galbanum, or am-
moniacum, which must be rubbed or ground till
they are dissolved ; then mix the whole with a
sufficient heat ; keep it in a phial stopt, and when
it is to be used set it in hot water.
A Cement for broke?! China^ Glasses, S^c.
Take quick-lime and white of eggs, or old thick
varnish ; grind and temper them well together.
Drying oil and white lead are also frequently
used for cementing china and earthen-ware ; but
this cement requires a long time to dry. Where it
is not necessary the vessels should endure heat or
moisture, isinglass glue, with a little tripoli, or
chalk, is better. The juice of garlic also forms a
strong cement, and the joining can scarcely be
perceived.
A Cement for Chemical Glasses that "will bear the Fire.
Mix equal quantities of wheat flour, fine pow-
dered Venice glass, pulverized chalk, with half the
quantity of fine brick dust, and a little scraped lint
in the whites of eggs : this mixture is to be spread
upon a linen cloth, and applied to the crack of the
glasses, and should be well dried before they are
put into the fire.
A Cement useful for Turners.
Take resin, one pound ; pitch, four ounces :
melt these together, and, while boiling hot, add
^yS CEMENTS.
brick-dust, until, by dropping u, little upon a stone,
you perceive it hard enough ; then pour it into
water, and immediately make it up in rolls, and it
is tit for use.
Another^ finer. — Take resin, one ouuce; pitch,
two ounces; add red ochre, finely powdered, until
you perceive it strong enough. Sometimes a small
quantity of tallow is used, according to the heat of
the weather, more being necessary in winter than
in summer.
Either of these cements is of excellent use for
turners. By applying it to tlie side of a chuck,
and making it warm before the fire, you may fasten
any thin piece of w^ood, which will hold while you
turn it ; when you want it off again, strike it on
the top with your tool, and it will drop ofi' imme-
diately.
A strong Cement f^r Electrical Purposes.
Melt one pound of resin in a pot or pan, over a
slow fire ; add to it as much plaster of Paris, in
fine powder, as will make it hard enough, then add
a spoonful of linseed-oil, stirring it all the while,
and try if it be hard and tough enough for your
purpose ; if it is not sufficiently hard, add more
plaster of Paris ; and if not tough enough, a little
more linseed-oil.
This is a very good cement for fixing the necks
of globes or cylinders of electrical machines,
or any thing else that requires to be strongly
fixed.
Another^ softer. — Take resin, one pound; bees-
wax, one ounce ; add to it as much red-ochre as
will make it of sufficient stiffness ; pour it into
10
CEMENTS. '2'fJ
water, and make it into rolls. This cement is
useful for cementing hoops on glasses, or any other
mounting of electrical apparatus.
A Cement for Glass-Grmders.
Take pitch, and boil it ; add to it sifted-vvood
ashes, and keep stirring it all the while, until you
have it of a proper temper : the addition of a
little tallow may be added, as you find necessary.
Another, for small work. — To four ounces of
resin add one- fourth of an ounce of bees-wax, and
four ounces of whiting, made previously red hot
and melt them together. The whiting should be
put in while hot, that it may not have time to im-
bibe moisture from the atmosphere.
Shell-lac is a very strong cement for holding
metals, glass, or precious stones, while cutting,
turning, or grinding them. The metal, &c. should
be warmed, to melt it. For fastening ruby cylin-
ders in watches, and similar delicate purposes, sheli-
lac is excellent.
To solder or cement broken Glass.
Broken glass may be soldered or cemented in
such a manner as to be as strong as ever, by inter-
posing between the parts, glass ground up like a
pigment, but of easier fusion than the pieces to be
joined, and then exposing them to such a lieat as
will fuse the cementing ingredient, and make the
pieces agglutinate without being themselves fused.
A glass for the purpose of cementing broken
pieces of fUnt glass, may be made by fusing some of
the same kind of glass previously reduced to
300 CEMENTS.
powder, ulong with a little red-lead and borax, or
with the borax only.
Cement for Derbyshire Spar and other Stones.
A cement for this purpose may be made with
about seven or eight parts of resin and one of bees-
wax, melted together with a small quantity of
plaster of Paris. If it is wished to make the ce-
ment fill up the place of any small chips that may
have been lost, the quantity of plaster must be in-
creased a little. When the ingredients are well
mixed, and the whole is nearly cold, the mass
should be well kneaded together. The pieces
of spar that are to be joined must be heated
until they will melt the cement, and then pressed
together, some of the cement being previously
interposed.
Melted sulphur applied to fragments of stones
previously heated by placing them before a fire,
to at least the melting point of sulphur, and then
joined with the sulphur between, makes a pretty
firm and durable joining.
Little deficiencies in the stone, as chips out of
corners, &c. may also be filled up with melted
sul})hur, in which some of the powder of the stone
has been melted.
A Cement that will stand against boiling Watery and
eve)i bear a considerable Pressure of Steam.
In joining the flanches of iron cylinders, and
other parts of hydraulic and steam engines, great
inconvenience is often experienced from the want
of a durable cement.
CEMENTS. SOI
Boiled linseed-oil, litharge, red and white lead,
mixed together to a proper consistence, and ap-
plied on each side of a piece of flannel previously
shaped to fit the joint, and then interposed be-
tween the pieces before they are brought home
(as the workmen term it) to their place by the
screws or other fastenings employed, make a close
and durable joint.
The quantities of the ingredients may be'varied
without inconvenience, only taking care not to
make the mass too thin with oil. It is difficult in
many cases instantly to make a good fitting of large
pieces of iron work, which renders it necessary
sometimes to join and separate the pieces repeated-
ly, before a proper adjustment is obtained. When
this is expected, the white-lead ought to predomi-
nate in the mixture, as it dries much slower than
the red. A workman, knowing this fact, can be at
little loss in exercising his own discretion in re-
gulating the quantities. It is safest to err on the
side of the white-lead, as the durability of the
cement is no way injured thereby, only a longer
time is required for it to dry and harden.
When the fittings w'ill not admit easily of so
thick a substance as flannel being interposed,
linen may be substituted, or even paper or thin
pasteboard.
This cement answers well also for joining broken
stones, however large. Cisterns built of square
stones, put together with this cement, will never
leak or want any repairs. In this case the stones
need not be entirely bedded in it : an inch, or
even less, of the edges that are to lie next the
water, need only be so treated ; the rest of the
joint may be filled with good lime.
302 CEMENTS.
Another Cement that will stand the Actio?! of Boiling
Water and Steam.
This cement, which is preferable even to the
former for steam-engines, is prepared as follows.
Take two ounces of sal ammoniac, one ounce
of flowers of sulphur, and sixteen ounces of cast
iron filings or borings. Mix all well together by
rubbing them in a mortar, and keep the powder
dry.
When the cement is wanted for use, take one
part of the above powder and twenty parts of
clean iron borings or filings, and blend them inti-
mately by grinding them in a mortar. Wet the
compound with water, and when brought to a con-
venient consistence, apply it to the joints with a
wooden or blunt iron spatula.
By a play of affinities, which those who are at
all acquainted with chemistry will be at no loss
io comprehend, a degree of action and re-action
takes place among the ingredients, and between
them and the iron surfaces, which at last causes
the whole to unite as one mass. In fact, after a
time, the mixture and the surfaces of the fianches
become a species of pyrites, holding a very large
proportion of iron, all the parts of which cohere
strongly together.
Blood Cement.
A cement often used by copper-smiths to lay
over the rivets and edges of the sheets of copper
in large boilers, to serve as an additional security
to the joinings, and to secure cocks, &c. from
leaking, is made by mixing pounded quick-lime
CEMENTS. .303
witli ox's blood. It must be applied fresh made,
as it soon gets hard.
\7e believe if the properties of this cement were
duly investigated, it would be found useful for many
purposes to which it has never yet been applied.
It is extremely cheap, and very durable.
Flour Faste.
Flour paste for cementing is formed principally
of wheaten flour boiled in water till it be of a glu-
tinous or viscid consistence.
It may be prepared of these ingredients simply
for common purposes, but when it is used by book-
binders, or for paper hangings, it is usual to mix
with the flour a flfth or sixth of its weight of
powdered alum ; and where it is wanted still more
tenacious, gum arable, or any kind of size, may be
added.
Japanese Cement ^ or Rice Glue,
This elegant cement is made by mixing rice
floiu' intimately with cold water, and then gently
boiling it. It is beautifully white, and dries
almost transparent. Papers pasted together by
means of this cement will sooner separate in their
own substance than at the joining, which makes
it extremely useful in the preparation of curious
paper articles, as tea trays, ladies' dressing boxes,
and other articles which require layers of paper
to be cemented together. It is in every respect
preferable to common paste made with wheat
flour, for almost every purpose to which that
article is usually applied. It answers well in par-
ticidar, for pasting into books the copies of writings
304 LUTES.
taken off by copying machines on unsized silver
paper.
With this composition, made with a small quan-
tity of water, that it may have a consistence simi-
lar to plastic clay, models, busts, statues, basso
relievos, and the like, may be formed. When dry,
the articles made of it are susceptible of a high
polish ; they are also very durable.
The Japanese make quadrille fish of this sub-
stance, which so nearly resemble those made of
mother of pearl, that the officers of our East India-
men are often imposed upon.
Of Sizes.
Common size is manufactured in the same man-
ner, and generally by the same people, as glue.
It is indeed glue left in a moister state, by discon-
tinuing the evaporation before it is brought to
a dry consistence, and, therefore, further par-
ticulars respecting the manufacture of it are
needless here.
Isinglass size may also be prepared in the man-
ner above directed for the glue, by increasing the
proportion of the water for dissolving it. And the
same holds good of parchment size.
I.UTES.
In many chemical operations the vessels must
be covered with something to preserve them from
the violence of the fire, from being broken or
melted, and also to close exactly their joinings
to each other, in order to retain the substances
which they contain, when they are volatile and
reduced to vapour.
LUTES. 805
The coating used for retorts, &c. to defend
them from the action of the fire, is usually com-
posed of nearly equal parts of coarse sand and re-
fractory clay. These matters ought to be well
mixed with water and a little hair, so as to form
a liquid paste, with which the vessels are covered
layer upon layer, till it is of the required thick-
ness. The sand, mixed witii the clay, is necessary
to prevent the cracks which are occasioned by the
contracting of the clay during its drying, which
it always does when pure. The hair serves also
to bind the parts of the lute, and to keep it ap-
plied to the vessel j for, notwithstanding the sand
which is introduced into it, some cracks are al-
ways formed, which would occasion pieces of it to
fall off.
The lutes with which the joinings of vessels are
closed are of different kinds, according to the nature
of the operations to be made, and of the substances
to be distilled in these vessels.
When vapours of watery liquors, and such as are
not corrosive, are to be contained, it is sufficient to
surround the joining of the receiver to the nose of
the alembic, or of the retort, with slips of paper, or
linen, covered with flour paste. In such cases,
also, slips of wet bladder are very conveniently
used.
When more penetrating and dissolving vapours
are to be contained, a lute is to be employed of
quick-lime slacked in air, and beaten into a liquid
paste with whites of eggs. This paste is to be
spread upon linen slips, which are to be applied
exactly to the joining of the vessels. This lute is
very convenient, easily dries, becomes solid, and
sufficiently firm.
VOL. ir. X
306 INK-MAKING.
Lastly, when saline acids, and corrosive vapours
are to be contained, we must then have recourse to
the lute called fat lute. This lute is made by form-
ing into a paste some dried clay, finely powdered,
sifted through a silken search, and moistened with
water; and then, by beating this paste well in a
mortar, with boiled linseed oil, that is, oil which
has been rendered dry by litharge dissolved in it,
this lute easily takes and retains the form given to
it. It is generally rolled into cylinders of a conve-
nient size. These are to be applied, by flattening
them to the joinings of the vessels, which ought to
be perfectly dry; because the least moisture would
prevent the lute from adhering. When the joinings
are closed with this fat lute, the whole is to be
covered with slips of linen, spread with lute of
lime and whites of eggs. These slips are to be
fastened with packthread. The second lute is ne-
cessary to keep on the fat lute, because the latter
remains soft, and does not become solid enough to
stick on alone.
INK-MAKING,
Inks are fluid compounds, intended to form
characters, or some other kinds of figures, on proper
grounds of paper, parchment, or such other sub-
stance as may be fit to receive them.
There are two principal kinds of ink, writing
and printing ink.
Writing Ink.
When to an infusion of gall-nuts some solution
of" sulphate of iron (green copperas) is added, a very
IMK-MAKING. SQJ
dark blue precipitate takes place. This precipitate
is the gallic acid of* the galls united to the iron of
the green vitriol, forming grdlat of iron, which is
the basis of writing ink. If galls and sulphate of
iron only were used, the precipitate would fall
down, leaving the water colourless ; and, in order
to keep it suspended in the water, forming a per-
manently black, or rather very dark blue fluid, gum
arable is added, which, by its viscid nature, pre-
vents the precipitate from falling down.
Various receipts have been given for the compo-
sition of writing ink, but very few have been
founded upon a knowledge of its real nature.
Though so important an article, it is but lately that
it has been studied with any attention ; and even
still, the principles and theory of its formation do
not appear to be so thoroughly understood as might
be wished. The receipt given by M. Ribancourt
is as follows: Take eiglit ounces of Aleppo galls,
in coarse powder; four ounces of logwood, in thin
chips ; four ounces of sulphate of iron (green cop-
peras); three ounces of gum arable, in powder;
one ounce of sulphate of copper (blue vitriol) ; and
one ounce of sugar-candy. Boil the galls and log-
wood together in twelve pounds of water for one
hour, or till half the liquid has been evaporated.
Strain the decoction through a hair sieve, or linen
cloth, and then add the other ingredients. Stir the
mixture till the whole is dissolved, more especially
the gum ; after whicii, leave it to subside for
twenty-four hours. Then decant the ink, and pre-
serve it in bottles of glass or stone-ware, well corked.
Red writing ink is made in the following manner :
Take of the raspings of Brazil wood a quarter of a
pound, and infuse them two or three days in vine-
gar. Boil the infusion for an hour over a gentle
X 2
308
INK-MAKING.
fire, and afterwards filter it while hot. Put it again
over the fire, and dissolve in it, first, half an ounce
of gum arabic, and afterwards of alum and white
sugar, each half an ounce.
Printing Ink.
Printers' ink is a black paint composed of lamp-
black and linseed or suet oil boiled, so as to acquire
considerable consistence and tenacity. The art of
preparing it is kept a secret ; but the obtaining good
lamp-black appears to be the chief difficulty in
making it.
The ink used by copper-plate printers, differs
from the last only in the oil not being so much
boiled, and the black which is used being Frank-
fort black.
Sympathetic Inks.
Sympathetic inks are such as do not appear
immediately after they are written with, but which
may be made to appear at pleasure, by certain
means. A variety of substances have been used
for this purpose. We shall describe the best
of them.
1. Dissolve some sugar of lead in water, and
write with the solution. When dry, no writing
■will be visible. When you want to make it appear,
wet the paper with a solution of alcaline sulphuret
(liver of sulphur), and the letters will immediately
appear of a brown colour. Even exposing the
writing to the vapours of these solutions will render
it apparent.
2. Write with a solution of gold in aqua regia,
and let the paper dry gently in the shade. Nothing
INK-MAKING. 309
will be seen ; but draw a sponge over it, wetted
with a solution of tin in aqua regia ; the writing
will immediately appear of a purple colour.
3. Write with an infusion of galls, and when
you wish the writing to appear, dip it into a
solution of green vitriol ; the letters will be black.
4. Write with diluted sulphuric acid, and nothing
will be visible. To render it so, hold it to the fire,
and the letters will instantly appear black.
5. Juice of lemons, or onions, a solution of sal
ammoniac, green vitriol, &c. will answer the same
purpose, though not so easily, or with so little
heat.
6. Green sympathetic ink. Dissolve cobalt in
nitro muriatic acid, and write with the solution.
The letters will be invisible till held to the fire,
when they will appear green, and will disappear
completely again when removed into the cold. In
this manner they may be made to appear and dis-
appear at pleasure.
A very pleasant experiment of this kind is to
make a drawing representing a winter scene, in
which the trees appear void of leaves, and to put
the leaves on with this sympathetic ink; then,
upon holding the drawing near to the fire, the
leaves will begin to appear in all the verdure of
spring, and will very much surprise those who are
not in the secret.
7. Blue sympathetic ink. Dissolve cobalt in
nitric acid ; precipitate the cobalt by potash ;
dissolve this precipitated oxyd of cobalt in acetic
acid, and add to the solution one-eighth of com-
mon salt.
This will form a sympathetic ink, that, when
cold, will be invisible, but will appear blue by heat.
X 3
310
REMOVING STAINS.
To remove Ink Stai)i6.
The stains of ink on cloth, paper, or wood, may
be removed by ahnost all acids; but those acids
are to be preferred which are least likely to injure
the texture of the stained substance. The muriatic
acid, diluted with five or six times its weight of
water, may be applied to the spot, and, after a
minute or two, may be washed off, repeating the
application as often as may be found necessary.
But the vegetable acids are attended witii less risk,
and are equally effectual. A solution of the oxalic,
citric (acid of lemons), or tartareous acids, in water,
maybe applied to the most delicate fabrics without
any danger of injuring them; and the same solu-
tions will discharge writing, but not printing ink.
Hence they may be employed in cleaning books
which have been defaced by writing on the margin,
without impairing the text. Lemon-juice, and the
juice of sorrels, will also remove ink stains, but notso
easily as tiie concrete acid of lemons, or citric acid.
To remove Iron Stains.
These may be occasioned either by ink stains,
v^hich, on the application of the soap, are clianged
into iron stains, or by the direct contact of rusted
iron. They may be removed by diluted muriatic
acid, or by one of the vegetable acids, already men-
tioned. When suffered to remain long on cloth,
they become extremely difficult to take out, because
the iron, by repeated moistening with water, and
exposure to the air, acquires such an addition- of
oxygen, as renders it insoluble in acid^. It luis
REMOVING STAINS. 311
been found, however, tliat even these spots may be
discharged, by applying first a solution of an alca-
line sulphuret, which must be well washed from
the cloth, and afterwards a liquid acid. The sul-
phuret, in this case, extracts part of the oxygen
from the iron, and renders it soluble in diluted
acids.
To 7'emove the Stains of Fruit mid Wine.
These are best removed by a watery solution of
the oxygenated muriatic acid, or by that of oxygen-
ated muriate of potash or lime, to which a little
sulphuric acid has been added. The stained spots
may be steeped in one of these solutions till it is
discharged; but the solution can only be applied
with safety to white goods, because the uncombined
oxygenated acid discharges all printed and dyed
colours. A convenient mode of applying the oxy-
genated acid, easily practicable by persons who
have not the apparatus for saturating water with
the gas, is as follows: Put about a table-spoonful of
muriatic acid (spirit of salt) into a tea-cup, and add
to it about a tea-spoonful of powdered manganese;
then set this cup in a larger one filled with hot
water ; moisten the stained spot with water, and
expose it to the fumes that arise from the tea-cup.
If the exposure be continued a sufficient length of
time, the stain will disappear.
To remove SjJOts of Grease Jrorn Cloth.
Spots of grease may be removed by a diluted
solution of potash ; but this must be cautiously
applied, to prevent injury to the cloth. Stains
of white wax, which sometimes fall upon the
X 1
312 removix:g stains.
clothes from wax candles, are removable by spirits
of turpentine, or sulphuric ether. The marks of
white paint may also be discharged by the last-
mentioned agents.
To take Spots of Grease out ofBookSy PiintSy or
Paper.
After having gently warmed the paper that is
stained with grease, wax, oil, or any other fat
body, take out as much as possible of it by means
of blotting paper ; then dip a small brush in the
essential oil of turpentine, heated almost to ebul-
lition (for when cold it acts only very weakly),
and draw it gently over both sides of the paper,
which must be carefully kept warm. This oper-
ation must be repeated as many times as the
quantity of the fat body imbibed by the paper, or
the thickness of the paper, may render necessary.
When the greasy substance is entirely removed,
recourse may be had to the following method to
restore the paper to its former whiteness, which is
not completely restored by the first process. Dip
another brush in highly rectified spirit of wine,
and draw it in like manner over the place which
was stained, and particularly round the edges, to
remove the border that would still present a stain.
By employing these means with proper caution,'
the spot will totally disappear, the paper will re-
sume its original whiteness, and if the process has
been employed on a part written on with common
ink, or printed with printer's ink, it will experience
no alteration.
<-'•
313
OF STAINING WOOD.
To stain Wood Yellow,
Take any white wood, and brush it over several
times with the tincture of turmeric root, made by
putting an ounce of turmeric, ground to powder,
to a pint of spirit, and after they have stood for
some days, straining off the tincture. If the yel-
low colour be desired to have a reddish cast, a
little dragon's blood must be added.
A cheaper, but less strong and bright yellow,
is, by the tincture of French berries made boiling
hot.
Wood may also be stained yellow by means of
aqua fortis, which will sometimes produce a very
beautiful yellow colour, but at other times a
browner. Care must be taken, however, that the
aqua fortis' be not too strong, otherwise a blackish
colour will be the result.
To stain Wood Red.
For a bright red stain for wood, make a strong
infusion of Brazil wood in stale urine, or water
impregnated with pearl-ashes, in the proportion of
an ounce to a gallon ; to a gallon of either of
which, the proportion of Brazil wood must be a
pound, which being put to them, they must stand
together for two or three days, often stirring the
mixture. With this infusion strained, and made
boihng hot, brush over the wood to be stained
till it appear strongly coloured ; then, while yet
3[i' STAINING WOOD.
wet, bi'usli it over with alum-water made in the
proportion of two ounces of alum to a quart of
water.
For a less bright red, dissolve an ounce of dra-
gon's blood in a pint of spirits of wine, and brush
over the wood with the tincture till the stain appear
to be as strong as is desired ; but this is, in fact,
rather lacquering than staining.
For a pink or rose red, add to a gallon of the
above infusion of Brazil wood two additional
ounces of the pearl-ashes, and use it as was before
directed : but it is necessary, in this case, to brush
the wood over with the alum-water. By increasing
the proportion of pearl-ashes, the red may be
rendered yet paler ; but it is proper, when more
than this quantity is added, to make the alum-water
stronger.
To slam Wood Blue.
W-ood may be stained blue by means either of
copper or indigo.
The method of staining blue with copper is as
ibllows : Make a solution of copper in aqua fortis,
and brush it w^iile hot several times over the
wood ; then make a solution of pearl-ashes in
the })ro])ortion of two ounces to a pint of water,
and brush it hot over the wood stained with the
solution of copper, till it be of a perfectly blue
colour.
To slain Wood Green.
Dissolve verdigrease in vinegar, or crystals of
verdigrease in water, and with the hot solution
brusji over llie wood till il, ])c duly stained.
10
STAINING WOOD. 315
To Stain Wood Purple.
Brash the wood to be stained several times willi
a strong decoction of logwood and Brazil, made
in the proportion of one pound of the logwood
and a quarter of a pound of the Brazil to a gallon
of water, and boiled for an hour or more. When
the wood has been brushed over till there be a
sufficient body of colour, let it dry, and then be
slightly passed over by a solution of one drachm
of pearl-ashes in a quart of water. This solution
must be carefully used, as it will gradually change
the colour from a brown red, which it will be
originally found to be, to a dark blue purple, and
therefore its effect must be restrained to the due
point for producing the colour desired.
To stain Jf^ood a Mahoganij Colour.
The substances used for staining mahogany
colour are madder, Brazil wood, and logwood ;
each of which produce reddish brown stains, and
they must be mixed together in such proportions
as will produce the tint required.
To stain Wood Black.
Brush the wood several times over with a hot
decoction of logwood. Then having prepared an
infusion of galls by putting a quarter of a pound of
}iowdered galls to two quarts of water, and setting
them in the simshine, or any other gentle heat,
for three or fx)ur days, brush the wood over three
or four times with it, and it will be of a beautiful
black. It may be polished with a hard brush and
shoemakers' black wax.
316
STAINING IVORY.
To stain Ivory Green.
Dissolve some copper or verdigrease in nitrous
acid, and soak the ivory in it.
To stain Ivory Yellow.
Put a quarter of a pound of alum in a pint of
water, boil the ivory in the solution ; then boil
it in a decoction of turmeric.
To stain Ivory Blue.
Boil it in the sulphate of indigo, and after-
wards in a solution of three ounces of white tar-
tar in a quart of water. Or it may be first stained
green, and then dipped into a solution of pearl-
ashes, made strong and boiling hot.
To stain Ivory Purple.
Put into nitrous acid one fourth of its weight
of sal ammoniac J soak the ivory in it.
MISCELLANEOUS.
To make Phosphorus.
Phosphorus was formerly prepared from urine,
and was therefore called phosphorus of urine ; but
it is exactly the same substance, from whatever
materials it is procured. The following is a pro-
cess for procuring it from bones, which consist
chiefly of Jime, combined with the phosphoric acid.
MISCELLANEOUS. Sl'J
Take a quantity of bones ; burn them to white-
ness in an open fire, and reduce them to a fine
powder. Upon three pounds of this powder, after
having been put into a matrass, pour two pounds
of concentrated sulphuric acid of commerce ; four
or five pounds of water must be afterwards added by
degrees, to assist the action of the acid. During
the process, the operator must place himself and
the vessel so that the fumes of the mixture may
be blown from him. The whole is then to be left
in a sand-bath for about twelve hours, or more,
taking care to supply the loss of water which
happens by evaporation. The next day, a large
quantity of water must be added; the clear hquor
must be decanted, and the rest strained through a
cloth or sieve. The residuary matter is to be
washed by repeated aflfusions of hot water till it
passes tasteless. The water which has been used
to wash out the adhering acid is mixed with the
decanted or strained liquor, and the whole fluid is
gradually evaporated in a flat earthen bason to the
consistence of a syrup. It is then mixed with an
equal weight of charcoal powder, and submitted to
distillation in an iron or earthen retort. Instead
of using a receiver, the neck of the retort may be
immersed in a bason of water, to a small depth,
and the phosphorus, as it comes over, will fall in
drops to the bottom.
Phosphorus made in this manner is blackish and
dirty ; it is purified by a second distillation. It
may also be prepared from urine by the following
method.
Dissolve as much lead in the nitric acid as it
will act upon, and the solution will be nitrate of
lead. Pour this into a quantity of urine, and a
precipitate will be formed. When no more pre-
318 MISCELLA\^EOUS.
cipitate falls clown by the addition of the solution,
suffer the whole to stand undisturbed till it has
all subsided, and then pour off the clear fluid.
Make this precipitate into a paste with charcoal
finely pounded, and dry it in an earthen pan gra-
dually. Then put the mass into an iron or
earthen retort, and distil it. The phosphorus
will come over, and may be collected under
water.
To make Canton\s Phosphortts.
Take some oyster-shells ; calcine them, by
keeping them in a good fire for about an hour.
Select out of the calcined shells the purest and
whitest parts, and pound and sift them. To
three parts of this lime add one of flowers of
sulphur ; mix tliem well together, and put them,
well pressed, into a crucible. Place it in a good
fire, where it must be kept red hot for an hour
at least ; it may then be taken out to cool. AVhen
it is cold, break the mass to pieces, and select out
of it the brightest part, which will shine in the
dark.
A beautiful representation of the telescopic
appearance of one of the planets may be made
by means of this. Cut out in paper the shape of
the planet, such as a half moon, Saturn and his
ring, &c., and cover it over with strong gum water;
then strew some of this phosphorus, finely pow-
dered, over the surface. When you Y/ant to
exhibit it in the dark, you must previously expose
it for a few minutes to the light of an Argand's
lamp ; or, what is better, make the flash from the
discharge of a large electrical jar, or battery, pass
over its surface, and it immediately becomes
MISCELLANEOUS. 319
Juminous, and exhibits a very exact resemblanc^e
of the planet.
To make Fhosiihor'ic Oil,
Put one part of pliosphonis into six of olive-oil,
and digest tiiem over a sand heat. The phosphorus
will dissolve. It must be kept v.ell corked.
This oil has the property of being very luminous
in the dark, and yet it has not sufficient heat to
burn any thing. If rubbed on the face and hands,
taking care to shut the eyes, the appearance is
most hideously frightful j all the parts with which
it has been rubbed appear to be covered with a
very luminous lambent flame of a bluish colour,
and the mouth and eyes appear in it as black spots.
There is no danger attending this experiment.
The light of it is sufficient to show the hour of the
night on. a watch, by holding it close to the bottle
when it is unstopped.
To make Phosphorated Lime,
Put a few grains of phosphorus into t!ie bottom
of a Florence flask, and fill it up with quick-hme.
Place it over a lamp till the phosphorus has sub-
limed, and is thoroughly mixed with the lime. If
any of this lime be thrown out in the dark, it has
the appearance of a shower of fire, but cannot burn
any thing, as the quantity of phosphorus is too
small to produce any sensible heat.
To make a Phosphoric Fii^e Bottle.
Take a very small phial, and put into it a bit
of phosphorus as large as a pea, and fill up the
S20 MISCELLANEOUS.
bottle with lime. Fix an iron vessel, as a shovel,
for instance, with common sand, and put it over
the fire. Set the phial in this sand, having loosely
stopped it with a cork. Stir about the ingredients
with a wire, and mix them together ; taking care
that the phosphorus does not catch fire by too
great an access of air. Keep the bottle in the
sand till the phosphorus is thoroughly incorpor-
ated with the lime, when it will be of a reddish
yellow.
This bottle is extremely convenient for pro-
curing an instantaneous light in the dark. For
this purpose, nothing more is necessary than to
uncork the bottle, and to introduce a brimstone
match, stirring it about a little, by which it will
catch fire and light.
The bottle must be always kept carefully cork-
ed, and opened as seldom as possible.
A more durable kind may be made by uniting
together one part of sulphur with eight of phos-
phorus. When this is used, a match is introduced
into it, and then rubbed upon a bit of cork.
To make Phosphuret of Lime.
Put half an ounce of phosphorus, cut into
small bits, into a glass tube about a foot long,
and half an inch in diameter, closed at one end.
Fill up with quick-lime grossly powdered, and
stop the mouth of the tube loosely. Heat that
part of the tube which contains the lime over a
chafing-dish, till it be red hot; and then apply
the heat of a lamp to the part containing the
phosphorus, which will sublime, and mix with the
MISCELLANEOUS. S^l
lime. When cooled, the mixture will be a reddish
mass.
If phosphuret of lime be dropped into water,
air bubbles will be disengaged, which, on bursting
at the top, will inflame with small explosions.
They consist of phosphorated hydrogen gas.
To make Fulminating Powder.
Triturate in a warm mortar three parts, by
weight, of nitre, two of mild vegetable alkali (car-
bonate of potash), and one of flowers of sulphur.
A few grains of this laid upon a knife, and held
over the candle, first fuses, and then explodes with
a loud report. A drachm of it put into a shovel,
and held over the fire, makes a noise as loud as a
cannon, and indents the shovel as if it had received
a violent blow.
To make Fulminating Mercury,
Dissolve 100 grains of mercury with heat, in
a measured ounce and a half of nitric acid. This
solution being poured cold upon two measured
ounces of alkohol, previously introduced into any
convenient glass vessel, a moderate heat is to be
applied till effervescence is excited. A white
fume then begins to undulate on the surface of the
liquor, and the powder will be gradually precipi-
tated on the cessation of action. The precipitate
is to be immediately collected on a filtre, well
washed with distilled water, and cautiously dried
in a heat not exceeding that of a water bath. The
immediate washing of the powder is material,
VOL. II. Y
322 MISCELLANEOUS.
because it is lialfle to the re-action of the nitric
acid ; and while any of the acid adheres to it, it is
very subject to the action of light. From 100
grains of mercury, about 120 or ISO of tlie powder
are obtained.
This powder, struck on an anvil with a hammer,
explodes with a stunning disagreeable report j and
with such force as to indent both the hammer and
the anvil. Three or four grains are as much as
ought to be used for such experiments.
To make the Arbor Diance^ or Tree of Diana.
Take half an ounce of fine silver, and two
drachms of mercury, and dissolve them separately
in a quantity of aqua fortis. When the solutions
are perfectly made, mix them together, and pour
them into a pint of common water, and stir it
about, that the whole may be well mixed. Keep
this preparation in a bottle well corked. In a glass
globe, or other vessel, put the quantity of a small
nut of the amalgam of silver with mercury, and
pour three or four ounces of the above liquor
over it. After some hours there will arise from
the little globular amalgam small branches, which,
by increasing, will form a beautiful kind of shrub
or tree of silver.
To make a Tree of Silver 07i Glass.
Put a few drops of the solution of silver in aqua
fortis on a piece of glass, and having formed a bit
of copper or brass-wire to represent a tree with its
s
:\irSCELLANF.OUS. 323
branches, but flat so as to lie upon the glass, lay
it in the liquid, and let it remain for an hour or
two. A beautiful vegetation will be perceived all
round the wire, which will nearly be covered by
it. This may be preserved by washing it very
carefully with water, and putting another glass
over it.
To produce a Tree of Lead.
Dissolve an ounce of sugar of lead in a quart of
clear water, and put it into a glass decanter or
globe. Then suspend in the solution, near the
top, a small piece of zinc of an irregular shape.
Let it stand undisturbed for a day, and it will
begin to shoot out into leaves, and apparently to
vegetate. If left undisturbed for a few days, it
will become extremely beautiful j but it must be
moved with great caution.
It may appear to those unacquainted with che-
mistry, that the piece of zinc actually puts out
leaves ; but this is a mistake, for if the zinc be ex-
amined, it will be found nearly unaltered. This
phenomenon is owing to the zinc having a greater
attraction for oxygen than the lead has ; conse-
quently, it takes it from the oxyde of lead, which
re-appears in its metallic state.
Arbor Mar^tiSy or Tree of Mars.
Dissolve iron filings in aqua fortis moderately
concentrated, till the acid is saturated ; then add
to it gradually a solution of fixed alcali, formerly
called oil of tartar per deliquium. A strong ef-
fervescence will ensue, and the iron, instead of
falling to the bottom of the vessel, will afterwards
Y 2
SM MISCELLANEOUS.
rise, so as to cover the sides, forming a multitude
of ramifications heaped one upon the other, which
will sometimes pass over the edge of the vessel,
and extend themselves on the outside with all
the appearance of a plant.
To change Iron apparently into Copper,
Dissolve some blue vitriol (sulphate of copper)
in v/ater, and dip into the solution a piece of
bright iron or steel ; in a few seconds it may be
taken out, when it will be apparently turned to
copper. This is a deception ; the iron is not
changed into copper ; it is only encrusted over
with that metal, as may be easily seen by removing
the copper by a file. The iron having a stronger
attraction for sulphuric acid than copper, it takes
the acid from the latter, which is consequently
precipitated. This process is used for obtaining
the copper from waters near mines that contain a
great quantity of that metal. Iron plates are put
into them, which become incrusted with copper,
which is scraped off.
To prepare the Precipitate ofCassius.
This beautiful purple colour is extremely useful
to enamellers and glass stainers. To make it, pro-
ceed as follows.
Dissolve some gold in aqua regia (nitro-muriatic
acid), and also dissolve some pure tin in diluted
aqua regia, and pour it into the solution of gold.
A purple powder will be precipitated, which must
be collected and washed in distilled water.
MISCELLANEOUS. S25
A Method q/^ Silvering Ivory,
Take a slip of ivory, immerse it in a weak solu-
tion of nitrate of silver, and let it remain in it till
the ivory has acquired a bright yellow colour ; then
take it out of the solution, and immerse it in a
tumbler of pure water, and expose it in the water
to the rays of a very bright sun. After the ivory
has been exposed to the sun's rays for about two
or three hours, it becomes black ; but on rubbing
it a little, the black surface will become changed
into one of silver. Although this coating of silver
is extremely thin, yet if the ivory be well impreg-
nated with the nitrate of silver, the solution will
penetrate to a considerable depth; and as fast as
the silver wears off from the surface of the ivory,
the nitrate below being exposed to the light, is con-
verted into silver, and the ivory retains its metallic
appearance.
To cover Ribbons with Gold by a Chemical Process.
Let ether stand over phosphorus for some weeks,
and some of the phosphorus will be dissolved.
Dissolve also some gold in aqua regia (nitro-mu-
riatic acid). Dip the ribbon, first, into the nitro-
muriatic solution, and then into the phosphorated
ether, and it will be covered with a firm coating of
gold.
The same efi'ect may be produced by exposing
the ribbon, after having dipped it into the solution
of gold, to a current of phosphorated hydrogen gas
for some days.
To prepare Aurum Musivum.
Aurum musivum is used by japanners, and for
many varnished works, as snuff-boxes, coaches, &c.
T 3
326
MISCELLANEOUS.
When well managed, it has all the beautiful ap-
pearance of gold in powder.
To make it, amalgamate twelve parts of the
purest tin with three parts of mercury. The amal-
gam must then be triturated in a stone mortar with
seven parts of flowers of sulphur, and three parts of
sal ammoniac. The mixture is then put into a
matrass, and the whole is exposed to a gentle sand
heat, until no more white fumes arise. When,
upon this, the heat is somewhat raised, cinnabar
sublimes, together with some oxygenated muriate
of tin ; while, at the same time, the remaining tin
unites with the remaining sulphur, and forms the
aurum musivum, exhibiting a golden yellow and
flakey or scaley matter, of a metallic lustre.
The main point in this process is the proper re-
gulation of the fire : when this is too strong, the
operation does not succeed j and instead of aurum
musivum, common sulphuret of tin is obtained.
To make an Artificial Volcano,
For this curious experiment, which in some re-
spects resembles the effect of volcanoes, we are
indebted to Lemery.
Mix equal parts of pounded sulphur and iron-
filings, and having formed the whole into a paste
with water, bury a quantity of it, forty or fifty
pounds, for example, at about the depth of a foot
below the surface of the earth. In ten or twelve
hours afterwards, if the weather be warm, the
earth will swell up and burst, and flames will issue
out, which will enlarge the aperture, scattering
around a yellow and blackish dust.
It is not impossible, that what is here seen in
miniature, takes place on a grand scale in volca-
MISCELLANEOUS. 327
noes ; as it is well known that they always furnish
abundance of sulphur, and also metallic substances
To produce Artificial Lightning,
Provide a tin tube, that is much larger on one
side than the other, and in which there are se-
veral holes. Fill this tube with resin, in powder,
and when it is shook over the flame of a torch, it
will prqduce a sudden corruscation that strongly
represents a flash of lightning. This is the manner
in which lightning is produced at the theatres : it
is not the flame itself that is to be seen, but its
reflection only, as happens for the most part in
nature.
In this manner also the flambeaux of the
furies on the stage are constructed, except that,
at the end of each of them, there is a match dipped
in spirits of wine ; by means of which it is only
necessary to shake them, and they will produce a
sudden and very considerable flame.
Method of cutting GlasSy by means of Heat,
Take a common wine-glass, or any vessel you
want cut, and having heated a poker in the fire till
it is almost red hot, but not quite, apply it to the
part where you wish the crack to begin ; having
held it upon the part for about a minute, remove
the poker, and wet the place: the glass will imme-
diately crack. Having now begun the crack, you
may lead it in any direction, by merely drawing the
hot poker in the direction you want. This is ex-
tremely useful in many chemical experiments,
where you are in want of proper apparatus.
Glass tubes may be easily cut with a file.
Y 4
3*i8 MISCELLANEOUS.
A Method ofjorming Pictures by Nitrate
of Silver.
It is well known that light has a powerful effect
upon many of the metallic oxydes, causing them to
turn black.
Mr. J. Wedgewood has availed himself of this
property, for copying paintings on glass, and making
profiles of figures, by means of nitrate of silver.
Cover white paper, or leather, with a solution of
nitrate of silver, and place it behind a painting on
glass, which is exposed to the rays of the sun. The
rays which come through will blacken the paper;
but the shades will be more or less deep, in propor-
tion to the quantities of light transmitted through
the different parts of the glass. Where the glass is
transparent, and all the light comes through, the
paper will be made quite black ; where the glass is
quite opaque, and does not transmit any light, tlie
paper will be quite white, and there will be degrees
of intensity of the shadow of every variety between
these.
This picture is not sensibly affected by the light
of candles or lamps; bat the day-light destroys it
very soon, causing all the paper to become black ;
nor have any means, hitherto tried for preventing
this, been successful.
Besides the application of this property of nitrate
of silver to copying the light and shadow of paint-
ings on glass, it may be applied to some others.
By means of it delineations may be made of all such
objects as are partly opaque and partly transparent.
The fibres of leaves, and the wings of insects, may-
be pretty accurately represented by it, by only
making the solar rays pasvS through them, upon
prepared leather or paper.
MISCELLANEOUS. o'2{)
Sir Humplirey Davy found, that the images of
small objects produced by means of the solar mi-
croscope, may be copied without difficulty on
prepared paper : the best proportion was one
part of nitrate to about ten of water. This is
sufficient to enable the paper to become tinged,
without hurting its texture.
Artificial Fire- Works.
Artificial fire-works are of two kinds — those
made of gunpowder, nitre, and other inflammable
substances and filings of the metals, camphor, &c.;
and those produced by hydrogen or inflammable air.
Those made with gunpowder are well known,
and are called rockets, fire-wheels, tourbillons, &c.
Of these, the most usual are rockets. They are
made by ramming into strong cylindrical paper cases
put into wooden moulds, like small hollow columns,
powdered gunpowder, or the ingredients of which it
is composed ; viz. saltpetre, sulphur, and charcoal,
very dry.
If you would represent a fiery rain falling from
the rocket, mix among your charge a composition
of powdered glass, filings of iron, and saw dust ; this
shower is called the peacock's tail, on account of the
various colours that appear in it. Camphor mixed
with the charge produces white or pale fire; resin
a reddish colour; sulphur a blue ; sal ammoniac a
green ; antimony a reddish yellow ; ivory shavings
a silvery white, pitch a deep or dark coloured fire,
and steel filings beautiful corruscations and sparks.
Sticks are fastened to the rockets by which they
are projected into the air, after they have been
lighted ; the charge, burning with great intensity
at one end, acts upon the air, which, in its turn,
5
330 MISCELLANEOUS.
re-acts upon the rocket, and causes it to ascend, on
the same principle as a boat is put off by a man in
it who pushes against the shore with a boat-hook.
Fire-works by means of infiammahle air are the
most elegant ; and being free from smell or smoke,
may be exhibited in a room without any disagree-
able effect.
By referring to what has been already said when
treating on hydrogen gas, the principle of these fire-
works will easily be understood. Small copper or
tin tubes must be provided, of about a quarter of
an inch in diameter ; these tubes must be formed
into the shapes required, and pierced with very
small holes where a flame is wanted to appear; to
these pieces must be attached large bladders, or
air-tight bags, filled with hydrogen gas. There
must also be a stop-cock between the tubes and
the bladders, to open or close the communication.
Having prepared every thing properly, open the
stop-cock, and press the bladders; the hydrogen
will be forced out through the holes in the tubes,
and by means of a taper may be inflamed. A con-
stant stream of fire may be kept up as long as
there is any air in the bladders.
Upon this principle were constructed the beau-
tiful fire-works exhibited in London by Mr. Cart-
wright.
The philosophical candle, formed by hydrogen,
has been already described under chemistry.
Of Artificial Gi^ottos and Shell-Work.
The idea of artificial grottos is often wrongly
conceived. They are usually intended as imita-
tions of nature; yet natural grottos are never seen
MISCELLANEOUS. 33i
ornamented within with shells, corals, pieces of
looking-glass, &c., disposed in a regular manner.
Sometimes, indeed, a more sober species of grotto
is attempted, composed of rough masses of stone,
representing natural rocks, and covered with moss,
and various plants. The difficLdties, however, in
this art, considered as an imitation of nature, are
much greater than most persons suppose. To suc-
ceed, the knowledge of the painter and the archi-
tect are necessary ; and only those who have been
accustomed to study nature with great attention,
are sufficiently acquainted with natural forms.
The chief aim should be to dispose the parts so that
one may forget that the arrangement is artificial.
There is another idea, however, that may be en-
tertained with regard to artificial grottos ; which
is, that they need not represent natural caverns;
but the supposed productions of enchantment or
magic. In this light, most of the incongruities
will disappear, and every possible license may be
given for the display of imagination and taste.
Nothing is supposed to be impossible to magical
power : therefore every species of natural or artifi-
cial productions may be combined together, and
every thing introduced that may excite astonish-
ment and surprise. Here there is no necessity for
imitating the appearance of natural grottos, but
every species of regularity and irregularity may be
licensed. The sciences of architecture and me-
chanics may thus lend their aid in the construction
of places, where mere nature is not the object of
imitation, but where every thing may be employed
that can have a powerful eft'ect upon the imagination.
Shell-work, corals, statues, fountains, streams of
water, paintings, curious musical pieces of mechan-
ism J in short, every thing extraordinary, may be
3S'i MISCELLANEOUS.
introduced with great success ; and in this art there
is an ample field for the display of taste.
The external of a grotto is the part where the
least attempt at ornament should be made. It is
best made to resemble some hermitage constructed
of roots of trees, or some similar kind of structure ;
but no attempt should be made to imitate a natural
cavern, except the situation should be peculiarly
happy for this purpose.
A cement for fixing large shell-work and stones
may be prepared as follows : Melt together a
quantity of resin, pitch, and bees-wax, and add
to it powdered marble or freestone, and a little
sulphur. Any of the finer cements, mentioned
under the article cements^ may be used for delicate
purposes.
To make Artificial Coral for Grottos.
To two drachms of fine vermilion add one
ounce of clear resin, and melt them together.
Having your branches or twigs peeled and dried,
paint them over with this mixture while hot. The
black thorn is the best branch for it. Hold them
over a gentle fire, turning them round till they
are perfectly covered and smooth. You may
make white coral with white lead, and black with
lamp-black.
To take Impressions from Leaves.
Take green leaves of trees or flowers, and lay
them between the leaves of a book till they are dry.
Then mix up some lamp-black with drying oil, and
make a small dabber of some cotton wrapped up in
a piece of soft leather. Put your colour upon a
MISCELLANEOUS. 333
tile, and take some on your dabber. Laying the dried
leaf flat upon a table, dab it very gently with the
oil colour, till the veins of the leaf are covered ;
but you must be careful not to dab it so hard as to
force the colour between the veins. Moisten a
piece of paper, or rather have a piece laying
between several sheets of moistened paper for
several hours, and lay this over the leaf which has
been blackened. Press it gently down, and then
subject it to the action of a press, or lay a heavy
weight on it, and press it down very hard. By
this means you obtain a very beautiful impression
of the leaf and all the veins ; even the minutest
will be represented in a more perfect manner than
they could be drawn with the greatest care. These
impressions may also be coloured in the same
manner as prints.
A Method of making Pictures of Birds, hy
means of their own Feather's.
Get a thin board or pannel of deal, or wainscot,
well seasoned, that it may not warp. Paste w^hite
paper over it, and let it dry. Take any bird that
you would wish to represent, and draw its outline
on the paper, in the attitude you desire, and of the
full size, adding what landscape, back ground, &c.
you wish. This outline, so drawn, is afterwards
to be filled up with the feathers from the bird,
placing each feather in that part of the drawing
corresponding to the part of the bird it was taken
from.
To do this, cover the representation with several
coats of strong gum water, letting it dry between
each coat, till it is of the thickness of a shilling-.
334) MISCELLANEOUS.
When your ground is thus prepared, take the
feathers off from the bird, beginning at the tail or
the points of the wings, as you must work upwards
towards the head. These feathers must be pre-
pared by cutting off all the downy part ; and the
larger feathers must have the insides of their shafts
pared off, to make them lie flat. To lay them on,
make use of a pair of small pliers to hold them by;
and moistening the gummed ground with water,
place each feather in its natural and proper situ-
ation. Keep each feather down, by putting a
small leaden weight upon it, till you have another
prepared to lay on. You must be careful not to
let the gum come through the feathers, as it smears
them, and sticking to the bottoms of the weights,
will be apt to pull the feathers off. When you
have put on all the feathers, you must cut a piece
of round paper, and colour it like the. eye, which
you may stick in its place j but the best way is to
get small eyes made of glass. The bill, legs, and
feet must be drawn and coloured from Nature.
When it is finished and adjusted to your mind, lay
a sheet of paper upon it, and upon that a heavy
weight to press itj which must remain till the
whole is quite dry.
To take the Impressmi of any Butterfly in ail
its Colours.
Having taken a butterfly, kill it wdthout spoiling
its wings, which contrive to spread out as regularly
as possible in a flying position ; then, with a small
brush or pencil, take a piece of white paper; wash
part of it with gum water, a little thicker than
ordinary, so that it may easily dry ; afterwards,
MISCELLANEOUS. 33.5
laying your butterfly on the paper, cut off tlie
body close to the wings, and throwing it away, lay
the paper on a smooth board, with the fly upwards ;
and laying another paper over that, put the whole
preparation into a screw press, and screw it down
very hard, or otherwise press it, letting it remain
under that pressure for half an hour. Afterwards
take off the wings of the butterfly, and you will
find a perfect impression of them, with all their
various colours marked distinctly, remaining on
the paper. When this is done, draw between the
wings of your impression the body of the butterfly,
and colour it after the insect itself.
' To lay Mezzo t into Prints upon Glass.
Take what mezzotinto print you please ; cut
off the margin, and lay it flat in a dish of clear hot
water ; let it remain on the surface till it sinks.
When you take it out, be careful not to break it,
and press it betwixt clean cloths or papers, so that
no water may appear on the surface, but the print
be quite damp : then lay it, face uppermost, on a
flat table ; have ready a plate of pure crown glass,
free from all spots or scratches ; lay some Venice
turpentine all over one side of it with a soft brush,
and hold it to the fire a little, to make it run quite
equal and thin ; then let it fall gently on the print.
Press it down, that the turpentine may stick to the
print ; and also press the print with your fingers,
from the middle to the edges of the glass, so that
no blisters may remain. Wet your print now with
a soft cloth, and rub it gently with your finger, and
the paper will peel off, leaving only the impression
3S6 MISCELLANEOUS.
npon the glass. When it is dry, wet it ever with
oil of turpentine till it is transparent, and set it by
to dry, when it will be fit for painting. The
colours used for painting in this manner are the
usual oil colours, and there is nothing in the pro-
cess particular.
To make Artificial Pearls.
Take the blai/ or bleak Jishy which is very com-
mon in the rivers near London, and scrape off the
fine silvery scales from the belly. Wash and rub
these in water. Then suffer this water to settle,
and a sediment will be found of an oily consistence.
A little of this is to be dropped into a hollow glass
bead of a bluish tint, and shaken about, so as to
cover all the internal surface. After this, the bead
is filled up with melted white wax, to give it solidity
and weight.
To prepare the Nuremberg Powder of variegated
Colour,
Mix together clean filings of copper, brass, iron,
steel, and other metals. Put each of them sepa-
rately into an iron vessel, and heat them till they
change colour. The degree of heat can only be
regulated by trial. Take these to a good flatting-
mill, furnished with a funnel at top, and pass these
filings through it, and you will procure a most
beautiful sparkling powder of all sorts of lively
colours.
MISCELLANEOUS. 337
To make very beautiful Artificial Petrifactions.
Put into a retort a quantity of pounded fluor
spar and a few bits of broken glass, and pour upon
them some sulphuric acid ; fluoric acid gas will
be disengaged, holding silex in solution. The
substances to be made to resemble petrifactions,
as lizards, frogs, branches of trees, birds nests, &c.
must now be moistened with water, and placed
in a vessel connected with the neck of the retort.
The fluoric acid gas will be absorbed by the
moisture adhering to the substances, and the silex
will be precipitated upon them like a sort of hoar-
frost, which will have a very beautiful appearance,
and is very durable.
A Method of making Cast Steel.
This method has been invented in France.
It is as follows : Take small pieces of iron, and
place them in a crucible, with a mixture of chalk
or lime-stone and the earth of Hessian crucibles.
Six parts of chalk and six of this earth must be
employed for twenty parts of the iron. The mat-
ters are to be so disposed, that, after fusion, the
iron must be completely covered by them, to pre-
vent it from coming into contact with the external
air. The mixture is then to be gradually heated,
and at last exposed to a heat capable of melting iron.
If the fire be well kept up, an hour will generally
be sufficient to convert two pounds of iron into
excellent and exceedingly hard steel, capable of
being forged ; an advantage not possessed by steel
made in the usual manner.
VOL. II. z
388
MISCELLANEOUS.
Method of distinguishing Iron from Steel.
Drop a little weak aqua-fortis on the metal ; let it
remain for a few minutes, and then wash it off with
water. If it is steel, the spot will be black, but if
iron, the spot will be whitish grey.
A Test for discovering the presence of Lead ^
Copper, 8^c, in Wines.
Lead and copper being sometimes used to
amend the taste of wines, and these metals being
of a very poisonous quality, a test that shall detect
this is of great value. The following test is the
discovery of Mr. Hanhemann.
Equal parts of oyster shells and crude sulphur
are to be kept in a white heat for a quarter of an
hour, and, when cold, this is to be mixed with
an equal quantity of acidulous tartrite of potash,
and put into a strong bottle with common water
for an hour, and then decanted into bottles holding
an ounce each, with twenty drops of muriatic acid
in each.
This liquor precipitates the least quantities of
lead, copper, &c. from wines, in a very sensible
black precipitate.
To make Pearl White.
Put some good aqua-fortis into a Florence flask,
and gradually add to it bismuth broken into small
pieces, till no more dissolves ; tlien let the solution
remain till it is transparent. Add to this some
MISCELLANEOUS. 339
water, and a white precipitate will be formed,
■which is to be washed and dried. This is white
oxyde of bismuth, commonly termed magistery of
hismuthy or pearl-xvhite.
This is used as a cosmetic, and is sold by the
perfumers ; but it very much impairs the skin,
blackening it by degrees, so that once used, it
itnist be continued ; and it is also to be feared,
that it has, besides, deleterious effects upon the
constitution.
To procure Anhnakiilce for the Mia^oscope.
The surface of infused liquors is generally
covered with a thin pellicle, which is easily broken,
but acquires thickness by standing ; the greatest
number of animalculas are generally to be found
in this superficial film.
To malce mi infusion of pepper. — Cover the bot-
tom of an open jar, about half an inch thick, with
common black pepper, bruised ; pour as much
soft water in the vessel as will rise about an inch
above the pepper. The pepper and water are
then to be well shaken together ; after which they
must not be stirred, but be left exposed to the air
for a few days, when a thin pellicle will be formed
on the surface of the water, containing miUions of
animal culae.
To procure the eels in paste. — Boil a little flour
and water till it becomes of a moderate consistence ;
expose it to the air in an open vessel, and beat it
together from time to time, to prevent the surface
from growing hard or mouldy : after a few days,
especially in summer time, it will turn sour ; then,
if it be examined with attention, you will find
myriads of eels on the surface. Apply them to
z 2
,340 MISCELLANEOUS.
the microscope on a slip of flat glass, first putting on
it a drop of water, taken up by the head of a pin,
for them to swim in.
A very usqful Method of breaking up Logs of
Wood,
The usual way of breaking up logs of wood for
the purposes of fuel, is by axes, and driving wedges
in. This, particularly in roots of trees, is very
laborious. It is also sometimes done by gun-
powder, in tlie same way as stones and rocks are
blasted j but this is very troublesome, as the plug
is often driven out. A better method of perform-
ing this operation has lately been invented. A
hole is bored with an augre, and a charge of pow-
der introduced. An iron screw, with a good
thread, having a hole bored through its axis, is then
introduced into the hole, and turned till it come
near to the powder. While the screw is putting
in, a wire is kept in the hole through its axis, but
it is afterwards drawn out, and a piece of twine
dipped in a solution of nitre is put into its place.
This quick match is set fire to, and by its slow
burning, affords time for the operator to retire be-
fore it sets fire to the gunpowder.
By this means, any roots or old stumps of trees
may be easily broken up.
A P?'Ocessfor purifying Fish Oil.
Take a gallon of crude stinking oil, and put to
it a pint of water poured off from two ounces of
lime slacked in the air; stir the mixture up
several times for the first twenty-four hours ; then
let it stand a day, and the lime water will sink
6
MISCELLANEOUS. 341
below the oil, which must be carefully separated
from it.
Another Method for purifying it more completely.
Take a gallon of crude stinking oil, and mix with
it a quarter of an ounce of powdered chalk, a
quarter of an ounce of lime slacked in the air, and
half a pint of water; stir them together; and when
they have stood some hours, add a pint of water,
and two ounces of pearl-ashes, and place the mix-
ture over a fire that will just keep it simmering,
till the oil appears of a light amber colour, and has
lost all smell, except a hot, greasy, soap-like scent.
Then superadd half a pint of water, in which one
ounce of salt has been dissolved, and having boiled
it half an hour, pour the mixture into a proper ves-
sel, and let it stand for some days, till the oil and
water separate.
If this operation be repeated several times, di-
minishing each time the quantity of ingredients
one-half, the oil may be brought to a very light
colour, and rendered equally sweet with the com-
mon spermaceti oil.
Oil purified in this manner is found to burn
much better, and to answer better the purposes of
the woollen manufacture. If an oil be wanted
thicker and more unctuous, this may be rendered
so by the addition of tallow or fat.
z J
142
FINE ARTS.
Under the name of Fine or Polite Arts, have
been generally comprehended, painting, sculpture,
architecture, poetry, and music: but in the com-
mon acceptation of words, the term line arts is usu-
ally confined to the three first; and the professors
of them are called, by way of eminence, artists.
It would exceed the limits to wliich we are con-
fined in this work, to descant on the value and im-
portance of the fine arts ; and it is the less neces-
sary, as this subject is beginning to be generally
understood, since drawing ha5 become a necessary
branch of education.
To treat fully and professionally on the fine arts,
would require a separate and extended work. What
is here proposed, is to consider that part which
enters into our system of usual school education.
Draining strictly means the delineation of the
contours or outlines of objects: and in this sense the
term is used by painters, who distinguish between
drawing and colouring : but the meaning of the
word drawing is not sufficiently restricted, since, in
common language, it has been applied to all such
paintings as are executed with water colours on
paper; the title of paintings having been rather
given to those executed with oil colours on canvass.
Since this difference of the materials only afforded
a very bad ground of distinction on which to found
two species, the term paintings in tcater colours has
very properly been lately introduced.
DRAWING. ~ 343
Still, however, in common language, the name of
drawings is given to all works in water-colours,
whether in outline only, in black and white, or in
colours ; and the term paintings to those in oil.
Painting in oil is capable of the greatest degree
of perfection, but is also the most difficult, and is
seldom attempted but by professional artists:
whereas, the use of water-colours is comparatively
easier, and better adapted for common use.
The first step in the arts is to learn to draw the
outlines of objects: next to express the light and
shadow: and, lastly, to add the colour.
But before we proceed, it will be necessary to
describe the implements and colours made use of.
Im'plemeyits for Dramng.
DroTdiing-boards are for jSxing the paper upon, so
that it may not shift, and also for straining it, to
prevent the colours, when laid wet upon the paper,
from causing it to swell up, so as to be uneven.
The simplest sort is made of a deal board framed
square, with a strong piece across each end, to
prevent warping. Upon this the paper may be
fixed down with pins, wafers, or sealing-wax, or it
may be strained with paste or glue, as follows :
having wetted the paper well with a sponge, lay it
upon the board, and turning up the edges about
half an inch, run a little good paste or glue all round
on the under side, and press the paper down upon
the board with a cloth; then set it by to dry : the
paper, which had expanded and blistered up much
when wet, will contract in drying, while the edges,
being fixed immoveably, will strain quite flat and
tight, and will be much better for drawing upon
than when loose.
z 4-
344 IMPLEMENTS FOR DRAWING.
The best kind of drawing-boards, however, are
made with a frame and a moveable pannel, upon
which the paper is simply put wet, and then
forced into the frame, where it is confined by
wedges at the back. This strains equally well
without the trouble of pasting, so that you may
dry it at the fire ; and it also looks much neater.
These drawing-boards may be bought at most
colour-shops. It is necessary to mention, that all
the angles of drawing-boards should be exactly
square.
Parallel rulers are for drawing parallel lines
readily : they are made of two pieces of ebony fas-
tened together by brass bars, so as always to move
parallel to each other. They may be bought of
different kinds and prices, at the mathematical
instrument makers.
Tee-squares are rulers made in the form of the
letter T, which are used with the drawing-boards ;
the short end, called the stock, being apphed to
the edge of the board, so as to slide forwards and
backwards ; while the long part, called the blade,
is used for drawing lines by. These are more con-
venient than parallel rulers, wlien a drawing-board
is used, as by them you draw lines at right
angles to each other at once, without using the
compasses.
Dividing compasses are instruments of brass and
steel, for dividing lines, and laying down measures
from scales, &c. : they are generally sold in cases,
containing also a steel pen for drawing lines cleaner
than can be done by a common pen, which is very
useful where neatness is required ; and points with
a black lead pencil, for putting into the compasses,
when circles are to be described. These cases
also contain scales of equal parts, and protractors
IMPLEMENTS FOR DRAWrNG. 34f5
for laying down angles. All these may be had at
the instrument makers.
Black lead pencils are made of plumbago sawed
into slips, and fitted into sticks of cedar. They are
of various qualities. The best are fine, without any
grit, not too soft, and that cut easily without break-
ing. An inferior kind is made by mixing up the
dust of plumbago with gum or glue, and thus form-
ing a composition, which is fitted into sticks in the
same manner as the best : these are always gritty,
and do not answer so well for most drawings ; yet,
being cheaper, they may be used upon many occa-
sions. It is necessary to examine pencils before
any quantity is bought, by cutting one of them,
because the composition pencils, having the same
outward appearance, are often sold for the best.
Indian rubber, or elastic gum, as it is also called,
is a substance much like leather, which has the
curious and useful property of erasing or defacing
lines drawn with black lead ; it is, therefore, much
used for this purpose. It is brought chiefly from
South America, in the form of small bottles, which
are cut up into slips. It is originally the juice of
a tree that grows very abundantly in Surinam, and
is like milk when exuded from the tree, but soon
becomes solid when exposed to the air. The na-
tives form balls of clay, which they smear over
with this milk : when this coating is almost dry,
they apply another, and so on, till it is of the re-
quired thickness ; they then moisten the clay with
water, which does not dissolve the Indian rubber,
and wash it out. These bottles are used by the
natives for containing water, or other liquors. It
is a production common to the East Indies also,
from whence it is imported in various forms.
34() IMPLEMENTS FOR DRAWING.
more convenient for use than the bottles above-
mentioned.
Indian Ink. — This very useful substance comes
from China, where it is used for common writing,
which is there performed with a brush instead of a
pen. It is a solid substance, of a brownish black
colour. When ground up with water upon a clean
tile or earthenware plate, it may be made either
lighter or darker, as required, by adding to it more
or less water. The best Indian ink is always
stamped with Chinese characters, breaks with a
glossy fracture, and feels smooth, and not gritty,
when rubbed against the teeth. The composition
is not accurately known. An inferior kind is made
in this country ; but it may be easily distinguished
by its grittiness. This is made of lamp black or
ivory black, ground up with gum.
Hair pencils are made of camel's hair, put into a
goose or swan's quill. To choose these, moisten
them a little, and if they come to a point without
splitting, they are good ; if they do not, they are
not fit for drawing with.
Charcoal is used for slightly sketching in the
outlines of figures, in order to get the proportions,
previous to making a drawing in chalk. The best
charcoal for this purpose is that of the willow ; it
is cut into slips, and the strokes made with it may
easily be rubbed out with a feather of goose's or
duck's wing.
Black chalk is a fossil substance resembling slaty
coal, which is cut into slips for drawing, it is
generally used in an instrument called a port
crayon, which is made either of steel or brass. It
is much employed for drawing figui'es, and is the
best substance i'or this purpose, in making drawings
IMPLEMENTS FOR DRAWING. 347
from plaster, or after the life. It is more gritty
than black lead, but is of a deeper black, and has
not the glossiness of the former. It is of two kinds,
French and Italian ; the former is soft, the latter
hard.
For mellowing and softening the shadows into
each other when black chalk is used,
Stumps are necessary. They are pieces of soft
shamoy leather, or blue paper, rolled up quite
tight, and cut to a point.
White chalk is used together with black, for
laying on the lights. This is different from com-
mon chalk, being much harder. Tobacco-pipe
clay will do very well instead of it.
Red chalk is a fossil substance of a red ochrey
colour, which is sometimes used for drawing, but
not so much now as it formerly was, the black
being preferred ; however, the red being cheaper,
will do very well for some purposes.
Drawing 'pape7\ — Any paper that will do for
writing will do for drawing ; but as the wire-marks
in common writing paper are injurious, paper
made without any wire-marks, called wove paper,
is generally used for this purpose. It is made of
various sizes and thickness.
Middle tint papier is paper of a brownish or of a
grey colour, which is used for drawing upon \\\t\\
black and white chalk. Being of a dark colour,
the strokes of the white chalk are distinctly seen ;
and it saves a great deal of time in making draw-
ings, as the tint of the paper answers for the half
shadow, so that all that is necessary to be done, is
to lay in the dark shadows and the lights.
348
GEOMETRY.
Various are the opinions upon the best modes
of beginning to learn to draw : and it is by no
means easy to decide upon this point, as so much
must always depend upon the genius, turn of mind,
and opportunities of the student. But, for general
purposes, and when circumstances will admit of it,
we have no hesitation in recommending to begin
by the study of geometry and perspective.
The' first forms the best introduction to a know-
ledge of form, by giving accurate ideas respecting
the most simple forms, of which all the others may
be considered as compounds : and the last is abso-
lutely necessary, not only to enable us to draw the
representations of regular objects, but even to see
them correctly : and it is certain that no one
unacquainted with its rules can ever attain the
power of drawing, without making the grossest
mistakes.
Geometry is a branch of mathematics which
treats of the description and properties of magni-
tudes in general.
Definitions or Ej^planations of Terms.
1. A point has neither length, breadth, nor
thickness. From this definition it may easily be
understood that a mathematical point cannot be
seen nor felt ; it can only be imagined. What is
commonly called a point, as a small dot made with
a pencil or pen, or the point of a needle, is not in
reahty a mathematical point ; for however small
such a dot may be, yet, if it be examined with a
magnifying glass, it will be found to be an irregular
GEOMETRY. 349
spot, of a very sensible length and breadth ; and
our not being able to measure its dimensions with
the naked eye, arises only from its smallness.
The same reasoning may be applied to every thi:ig
that is usually called a point ; even the point of
the finest needle appears like that of a poker when
examined with the microscope.
2. A li?ie is length, without breadth or thick-
ness. What was said above of a point, is also ap-
plicable to the definition of a line. What is drawn
upon paper with a pencil or pen, is not, in fact, a
line, but the representation of a line. For how-
ever fine you may make tliese representations, they
will still have some breadth. But by the defini-
tion, a line has no breadth whatever ; yet it is im-
possible to draw any thing so fine as to have no
breadth. A line, therefore, can only be imagined.
The ends of a line are points.
o. Parallel lines are such as always keep at the
same distance from each other, and which, if pro-
longed ever so far, would never meet. PI. 3.
Fig. 1.
4. A right line is what is commonly called a
straight line, or that tends every where the same
way.
5. A curve is a line which continually changes
its direction between its extreme points.
6. An angle is the inclination or opening of two
lines meeting in a point. Fig. 2.
7. The lines A B, and B C, which form the an-
gle, are called the legs or sides ; and the point
B where they meet, is called the vertex of the
angle, or the aiigular point. An angle is some-
times expressed by a letter placed at the vertex,
as the angle B, Fig. 2 : but most commonly by
three letters, observing to place in the middle the
350 GEOMETRY. •
letter at the vertex, and the other two at the end of
each leg, as the angle ABC.
8. When one line stands upon another, so as
not to lean more to one side than to another, both
the angles which it makes with the other are called
right-angles^ as the angles ABC and A B D, Fig. 3,
and all right-angles are equal to each other, being
all equal to 90° ; and the line A B is said to he per-
pendicular to C D.
Beginners are very apt to confound the terms
perpe?idiculary SLXid plumb or vertical line. A line is
vertical when it is at right-angles to the plane of
the horizon, or level surface of the earth, or to the
surface of water, which is always level. The sides
of a house are vertical. But a line may be per-
pendicular to another, whether it stands upright or
inclines to the ground, or even if it lies flat upon it,
provided only that it makes the two angles formed
by meeting with the other line equal to each other ;
as for instance, if the angles ABC, and A B D be
equal, the line AB is perpendicular to CD, what-
ever may be its position in other respects.
9. When one line, BE (Fig. 3), stands upon
another, C D, so as to incline, the angle E B C,
which is greater than a right-angle, is called an
obtuse angle ; and that which is less than a right-
angle, is called an acute angle, as the angle E B D.
10. Two angles which have one leg in common,
as the angles ABC, and ABE, are called co/i/i-
guous angles, or adjoining angles j those which
are produced by the crossing of two lines, as the
angles E B D and CBF, formed by C D and E F,
crossing each other, are called opposite or vertical
angles.
11. A^^'?^r^ is a bounded space, and is either a
surface or a solid.
GEOMETRY. 351
IS. A superficies, or surface, has length and
breadth only. The extremities of a superlicies are
lines.
A plane, or plane surface, is that which is
every where perfectly flat and even, or which will
touch every part of a straight line, in whatever
direction it may be laid upon it. The top of
a marble slab, for instance, is an example of
this, which a straight edge will touch in everv
point, so that you cannot see light any where
between.
A curved surface is that which will not coincide
with a straight line in any part. Curved surfaces
may be either convex or concave.
A convex surface is when the surface rises up in
the middle, as, for instance, a part of the outside
of a globe.
A concave surface is when it sinks in the middle,
or is hollow, and is the contrary to convex.
A surface may be bounded either by straight
lines, curved lines, or both these.
13. Every surface bounded by straight lines
only, is called a rectilinear fgure.
14. Three is the fewest number of sides that a
rectilinear figure can have ; and it is then called a
triangle.
15. Triajigles are of different kinds, according
to the lengths of their sides.
An equilateral triangle has all its sides equal, as
A B C, Fig. 4.
An isosceles triangle has two equal sides, as
D E F, Fig. 5.
A scalene triangle has all its sides unequal, as
G H I, Fig. 6.
16. Triangles are also denominated according
to the angles they contain.
352 GEOMETRY.
A inght-angled triangle is one that has in it a
right-angle, as A B C, Fig. 7.
A triangle cannot have more than one right-an-
gle. The side opposite to the right-angle B, as
AC, is called the h^pothenusef and is always the
longest side.
An obtuse-angled triangle has one obtuse angle,
as Fig. 8.
An acute-angled triangle has all its angles acute,
as Fig. 4.
An isosceles, or a scalene triangle, may be
either right-angled, obtuse, or acute.
Any side of a triangle is said to subtend the
angle opposite to it : thus A B (Fig. 7), subtends
the angle A C B.
If the side of a triangle be drawn out beyond
the figure, as A D (Fig. 8), the angle A, or CAB,
is called an internal angle, and the angle CAD,
or that without the figure, an external 2ing\e.
17. A figure with four sides is called a quadri-
lateral %ure. They are of various denominations,
as their sides are equal or unequal, or as all their
angles are right angles or not.
18. Every four-sided figure whose opposite sides
are parallel, is called a parallelogram. Provided
that the sides opposite to each other be parallel, it
is immaterial whether the angles are right or not.
Fig. 9, 10, 11, and 12, are all parallelograms.
When the angles of a parallelogram are all
right angles, it is called a rectangular parallel-
ogram, or a rectangle y as Fig. 11 and 12.
19. A rectangle may have all its sides equal, or
only the opposite sides equal. When all its sides
are equal, it is called a square^ as Fig. 12.
20. When the opposite sides are parallel, and all
the sides equal to each other, but the angles not
GEOMETRY. 8.53
riglit angles, the parallelogram is called a rhomhiiSy
as Fig. 10.
21. A parallelogram liaving all its angles oblique,
and only its opposite equal, is called a rhomboid^
as Fig. 9.
22. When a quadrilateral or four-sided figure
has none of its sides parallel, it is called a traj)e-
zhim, as Fig. 13. ; consequently every quadrangle,
or quadrilateral which is not a parallelogram, is a
trapezium.
23. A trapezoid has only one pair of its sides
parallel, as Fig. 14.
24. A diagonal is a right line drawn between
any two angles that are opposite in a quadrangle,
as I K, Fig. 15. In parallelograms the diagonal is
sometimes called the diameter^ because it passes
through the centre of the figure.
25. Co7nplements of a parallelogram. If any
point, as E (Fig. 15.), be taken in the diagonal of a
parallelogram, and through that point two lines are
drawn parallel to the sides, as A B, C D, it will be
divided into four parallelograms, D D, L, F, G G.
The two divisions, L, F, through which the diame-
ter does not pass, are called the complements.
26. Figures having more than four sides are
called polygons. If the sides are all equal, they
are called regidar polygons: if they are unequal,
they are called irregular polygons.
A pentagon is a polygon of five sides.
A hexagon has six sides.
A heptagon seven sides.
An octagon eight sides.
A nonagon nine sides.
An undecagon eleven sides.
A duodecagon twelve sides.
VOL. IT. A A
354 GEOMETRY.
When they have a greater number of sides, they
are called polygons of 13 sides, of 14 sides, and
so on.
27. Base of a figure is the side on which it is
supposed to stand erect, as A B and C D. (Fig. 16.)
28. Altitude of a figure is its perpendicular
height from the base to the highest part, as E F.
(Fig. 16.)
29. Area of a plane figure, or other surface,
means the quantity of space contained within its
boundaries, expressed in square feet, yards, or any
other superficial measure.
30. Similar Jigures are such as have the same
angles, and whose sides are in the same proportion,
as Fig. 17.
31. Equal figures are such as have the same
area or contents.
32. A circle is a plane figure, bounded by a
curve line returning into itself, called its circum-
ference, ABCD, (Fig. 18.) every where equally
distant from a point E within the circle, which is
called the centre.
33. The radius of a circle is a straight line drawn
from the centre to the circumference, as E F.
(Fig. 18.) The radius is the opening of the com-
pass when a circle is described \ and consequently
all the radii of a circle must be equal to each other.
34. A diameter of a circle is a straight line
drawn from one side of the circumference to the
other through the centre, as C B. (Fig. 18.) Every
diameter divides the circle into two equal parts.
35. A segment of a circle is a part of a circle cut
off by a straight line drawn across it. This straight
line is called the chord. A segment may be either
equal to, greater, or less than a semicirckf which is
GEOMETRY. 355
a segment formed by the diameter of the circle, as
C E B, and is equal to half the circle.
36. A tangent is a straight line drawn so as
just to touch a circle without cutting it, as G H.
(Fig. 18.) The point A, where it touches the cir-
cle, is called the point of contact. And a tangent
cannot touch a circle in more points than one.
37- A sector of a circle is a space comprehended
between two radii and an arc, as B I K. (Fig. 19.)
3S. The circumference of every circle, whether
great or small, is supposed to be divided into 360
equal parts, called degrees ; and every degree into
()0 parts, called minutes ; and every minute into
60 seconds. To measure the inclination of lines
to each other, or angles, a circle is described
round the angular point as a centre, as IK, Fig. 19.;
and according to the number of degrees, minutes,
and seconds, cut off by the sides of the angle, so
many degrees, minutes, and seconds, it is said to
contain. Degrees are marked by °, minutes by ',
and seconds by "; thus an angle of 48 degrees,
15 minutes, and 7 seconds, is written in this
manner, 48° 15' 7".
S9. A solid is any body that has length, breadth,
and thickness : a book, for instance, is solid, so is
a sheet of paper ; for though its thickness is very
small, yet it has some thickness. The boundaries
of \ solid are surfaces.
40. Similar solids are such as are bounded by an
equal number of similar planes.
41. A prism is a solid, of which the sides are
parallelograms, and the two ends or bases are
similar polygons, parallel to each other. Prisms
are denominated according to the number of angles
in the base, triangular prisms, quadrangular, pent-
angular, and so on, as Fig. 20, 21, 22, 23. If the
A A 2
SrA) GEOMETRY.
sides are perpendicular to the plane of the base, it is
called an iqnight prism ; if they are inclined, it is
called an oblique prism.
4f^. When the base of a prism is a parallelogram,
it is called a paralleloplpedony as Fig. !22. and 23.
Hence a parallelopipedon is a solid terminated by
six parallelograms.
43. When all the sides of a parallelopipedon are
squares, the solid is called a cube, as Fig. 23.
44. A rhomboid is an oblique prism, whose bases
are parallelograms. (Fig. 24.)
45. A pyramid, A B, (Fig. 25. and 26.) is a solid
bounded by, or contained within a number of
planes, whose base may be any rectilinear figure,
and whose faces are triangles terminated in one
point, B, commonly called the summit, or vertecc of
the pyramid.
When the figure of the base is a triangle, it is
called a triangular pyramid ; when the figure of
the base is quadrilateral, it is called a quadrilateral
pyramid, &c.
A pyramid is either regular or irregular, ac-
cording as the base is regular or irregular.
A pyramid is also right or ujnight, or it is
oblique. It is right, when a line drawn from the
vertex to the centre of the base, is perpendicular
to it, as Fig. 25. ; and oblique, when this line in-
clines, as Fig. 2(5.
46. A cylinder is a solid (Fig. 27. and 28.) ge-
nerated or formed by the rotation of a rectangle
about one of its sides, supposed to be at rest ; this
quiescent side is called the aiis of the cylinder.
Or it may be conceived to be generated by the
motion of a circle, in a direction perpendicular to
its surface, and always parallel to itself.
GEOMETRY. 357
A cylinder is either right or oblique^ as the axis
is perpendicular to the base or inclined.
Every section of a right cylinder taken at right
angles to its axis is a circle ; and every section
taken across the cylinder, but oblique to the axis,
is an ellipsis.
As a circle may be considered to be a polygon of
an infinite number of sides, so a cylinder may be
conceived as a prism having such polygons for
bases.
47. A cone is a solid, (Fig. 29. and 30.) having
for its base a circle, and its sides a convex surface,
and terminating in a point A called the vertex' or
apex of the cone. It may be conceived to be
generated by the revolution of a right-angled
triangle about its perpendicular.
A line drawn from the vertex to the centre of
the base, is the axis of the cone.
When this line is perpendicular to the base, the
cone is called an upright or right cone ; but when
it is inclined, it is called an oblique cone.
If a cone be cut through the axis from the vertex
to the base, the section will be a triangle.
If a right cone be cut by a plane at right angles
to the axis, the section will be a circle.
If a cone be cut oblique to the axis, and quite
across from one side to the other, the section will
be an ellipsis, as Fig. 31. A section of a cylinder
made in the same manner, is also an ellipsis j and
this is easily conceived ; but it does not appear so
readily to most people, that the oblique section of
a cone is an ellipsis : they frequently imagine that
it will be wider at one end than the other, or what
is called an oval^ which is of the shape of an e^^.
But that this is a mistake, any one may convince
himselij by making a cone, and cutthig it acros:-
A A 3
35S GEOMETRY.
obliquely : it will be then seen that the section, in
whatever direction it is taken, is a regular ellipsis ;
and this is the case, whether the cone be right or
oblique; except only in one case in the oblique cone,
which is when the section is taken in a particular
direction which is called sub-contrary to its base.
48. When the section is made parallel to one of
the sides of the cone, as Fig. 32., the curve ABC,
which bounds the section, is called a _;^Mr<7Z»o/«.
49. When the section is taken parallel to the
axis, as Fig. 33., the curve is called an hyperbola.
The curves which are formed by cutting a cone
in different directions are called conic sectmis, and
have various properties which are of great import-
ance in astronomy, gunnery, perspective, and
many other sciences.
50. A sphere is a solid, terminated by a convex
surface, every point of which is at an equal distance
from a point within called the centre. Fig. 34.
It may be conceived to be formed by making a
semicircle revolve round its diameter. This may
be illustrated by the process of forming a ball of
clay by the potter's wheel, a semicircular mould
being used for the purpose. The diameter of the
semicircle round which it revolves is called the
aa:is of the sphere.
The ends of the axis are called 2)oles.
Any line passing tlirough the centre of the
sphere, and terminated by the circumference, is a
diameter of the sphere.
Every section of a sphere is a circle ; every sec-
tion taken through the centre of the sphere, is
called a great circle^ as A B, Fig. 34. ; every other
is a lesser circle, as C D.
Any portion of a sphere cut off by a plane is
called a segment; and when the plane passes
GEOMETRY. 359
through the centre, it divides the sphere into two
equal parts, each of which is called a hemisphere.
51. A conoid is a solid produced by the circum-
volution of a section of the cone about its axis ;
and consequently may be either an elliptical conoidy
a hyperbolical conoid y or ^ parabolical co7ioid. When
it is elliptical, it is generally called a spheroid.
These solids are also called ellipsoid^ hj/perboloid,
and paraboloid.
52. A spheroid is a solid (Fig. 35.) generated
by the rotation of a semi-eliipsis about the trans-
verse or conjugate axis; and the centre of the
ellipsis is the centre of the spheroid.
The line about which the ellipsis revolves, is
called the adis. If the spheroid be generated,
about the conjugate axis of the semi-ellipsis, it is
called ^prolate spheroid.
If the spheroid be generated by the semi-ellipsis,
by revolving about the transverse axis, it is called
an oblong spheroid.
Every section of a spheroid is an ellipsis, except
when it is perpendicular to that axis about which
it is generated ; in which case it is a circle.
All sections of a spheroid parallel to each other
are similar figures.
A frustum of a solid means a piece cut off from
the solid by a plane passed through it, usually
parallel to the base of the solid ; as the frustum of
a cone, a pyramid, &c.
There is a lower and an upper frustum, according
as the piece spoken of does or does not contain the
base of the solid.
53. Ratio is the proportion which one magnitude
bears to another of the same kind, with respect to
quantity j and is usually marked thus, A : B.
A A 4
360 GEOMETRY.
Of these, the first is called the mUecedejit, and
the second the consequent.
The measure or quantity of a ratio is conceived
by considering what part of the consequent is the
antecedent ; consequently it is obtained by dividing
the consequent by the antecedent.
54. Three magnitudes or quantities, A,B,C, are
said to be proportional, when the ratio of the first to
the second is the same as that of the second to the
third. Thus, % 4, 8, are proportional, because 4
is contained in 8 as many times as 2 is in 4.
55. Four quantities, A,B,C,D, are said to be p>i'0'
portional when the ratio of the first A to the second
B is the same as the ratio of the third C to the
fourth D. It is usually written A : B : : C : D,
or, if expressed in numbers, 2:4 : : 8:16.
66. Of three proportional quantities, the middle
one is said to be a 7nea?i proportional between the
other two ; and the last a third proportional to the
first and second.
57. Oi'Jbur proportional quantities, the last is
said to be a fourth proportional to the other three,
taken in order.
58. Ratio of equality is that which equal -numbers
bear to each other.
59. Inverse ratio is when the antecedent is made
the consequent, and the consequent the antecedent.
Thus if 1 : 2 : : 3 : 6 ; then inversely, 2:1 \'.6\o.
60. Alternate proportion is when antecedent is
compared with antecedent, and consequent with
consequent. Thus if 2 : 1 : : 6 : 3j then by alter-
nation, 2 : 6 : : 1 : 3.
61. Proportion by composition is when the ante-
cedent and consequent, taken as one quantity, are
compared either with the consequent or with the
antecedent. Thus if 2 : 1 : : 6 : 3 ; then by com-
position 2 + 1 : 1 : : 6 -f 3 : 3, and 2 + 1:2:6+3:6.
9
GEOMETRY. 36i
CS. Divided proportion is when the difterence of
the antecedent and consequent is compared either
with the consequent or with the antecedent. Thus
if S : 1 : : 12 : 4 ; then by division 3 — 1:1: : 12
— 4 : 4 and 3 — 1 : 3 ::12 — 4 : 12.
i53. Continued proportion is when the first is to the
second as the second to the third ; as the tliird to
the fourth ; as the fourth to the fifth ; and so on.
64. Componnd ratio is formed by the muItipHca-
tion of several antecedents and the several conse-
quents of ratios together, in the following manner :
If A be to B as 3 to 5, B to C as 5 to 8, and C to
D as 8 to 6 ; then A will be D, as z:^^ = i ;
that is, A : D : : 1 : 2.
Q5. To Bisect means to divide any thing into
two equal parts.
QQ. To Trisect is to divide any thing into three
equal parts.
67. To Inscribe is to draw one figure within
another, so that all the angles of the inner figure
shall touch either the angles, sides, or planes of the
external figure.
68. To Circumscribe is to draw a figure round
another, so that either the angles, sides, or planes
of the circumscribed figure shall touch all the
angles of the figure within it.
69. A Rectangle under any two lines means a
rectangle which has two of its sides equal to one of
the lines, and two of them equal to the other. Also
the rectangle under AB,CD, means ABxCD.
70. Scales of equal parts. A scale of equal parts
is a straight line divided into any number of equal
parts at pleasure. Each part may represent any
measure you please, as an inch, a foot, a yard, &c.
One of these is generally subdivided into parts of
the next denomination, or into tenths or hundredths.
362 GEOMETRY.
Scales may be constructed in a variety of ways.
The most usual manner is to make an inch, or some
aliquot part of an inch to represent a foot ; and
then they are called inch scales, three-quarter-
inch scales, half-inch scales, quarter-inch scales, &c.
They are usually drawn upon ivory or box-wood.
71. An aa:iom is a manifest truth, not requiring
any demonstration.
72. Postulates are things required to be granted
true, before we proceed to demonstrate a propo-
sition.
73. A proposition is when something is either
proposed to be done, or to be demonstrated, and is
either a problem or a theorem.
74-. A problem is when something is proposed to
be done ; as some figure to be drawn.
75. A theorem is when something is proposed to
be demonstrated or proved.
76. A lemma is when a premise is demonstrated,
in order to render the thing in hand the more easy.
77. A corollary is an inference drawn from the
demonstration of some proposition.
78. A scholium is when some remark or observa-
tion is made upon something mentioned before.
79. The sign = denotes that the quantities be-
twixt which it stands are equal.
80. The sign -f denotes that the quantity after
it is to be added to that immediately before it.
81. The sign — denotes that the quantity after
it is to be taken away or subtracted from the quan-
tity preceding it.
Geometrical Problems,
Prob.l. To divide a given line, AB(P1. 4.),
into two equal parts.
GEOMETRY. 363
From the points A and B as centres, and with
any opening of the compasses greater than half
A B, describe arches cutting each other in c and d.
Draw the hne c d ; and the point E, where it cuts
A B, will be the middle required.
Prob. 2. To raise a perpendicular to a given line
A B, from a point given at C.
Case 1. When the given point is near the middle
of the line. On each side of the point C, take any
two equal distances C ^ and Ce; from d and e,
with any radius or opening of the compasses greater
than C df or C e, describe two arcs cutting each
other in Jl Lastly, through the points^ C, draw
the line J^C, and it will be the perpendicular re-
quired.
Case 2. When the point is at or near the end of
the line. Take any point d, above the line, and
with the radius or distance dCy describe the arc
e CJf cutting A B in e and C. Through the centre
d, and the point e, draw the line e df, cutting the arc
e Cfinf. Through the points^ C, draw the line
fC, and it will be the perpendicular required.
Prob. 3. From a given point f, to let fall a per-
pendicular upon a given line A B.
From the point J^ with any radius, describe
the arc de^ cutting A B in e and d. From the
points e dy with the same or any other radius,
describe two arcs cutting each other in g. Through
the points yand g\ draw the liney^'; andjTC will
be the perpendicular required.
Prob. 4. To make an angle equal to another
angle which is given, as « B ^.
From the point B, with any radius, describe the
arc a b, cutting the legs B «, B Z), in the points a
and b. Draw the line D e, and from the point D,
with the same radius as before, describe the arc ej^
364f GEOMETRY.
cutting T) e in e. Take the distance b c/, and apply
it to the arc ej", from e tof. Lastly, through the
points, T),J] draw the line D^ and the angle e T>f
will be equal to the angle b B a, as was required.
Prob. 5. To divide a given angle, ABC, into
two equal angles.
From the point B, with any radius, describe the
arc A C. From A and C with the same, or any
other radius, describe arcs cutting each in d. Draw
the line B d, and it will bisect the angle ABC, as^
was required.
Prob. 6. To lay down an angle of any number
of degrees.
There are various methods of doing this. One
is by the use of an instrument called a 2^rottYwtor,
which is a semicircle of brass having its circumfer-
ence divided into degrees. Let A B be a given
line ; and let it be required to draw from the an-
gular point A, a line making with A B any number
of degrees, suppose 20. Lay the straight side of
the protractor along the line AB, and count 20°
from the end B of the semicircle ; at C, which is
20* from B, make a mark ; then, removing the
protractor, draw the line A C, which makes with
A B the angle required.
Or, it may be done by a divided line, usually
drawn upon scales, called a line of chords. Take
60° from the line of chords in the compasses ; and
setting one at the angular point B, Prob. 4, with
that opening as a radius, describe an arch, as a b :
then take the number of degrees you intend the
angle to be of, and set it from b to a, then is « B ^,
the angle required.
Prob. 7' Through a given point C, to draw a
line parallel to a given line A B.
GEOMETRY. S65
Case 1. Take any point cf, in A B ; upon d and
C, with the distance C d, describe two arcs, e C,
and djl cutting the line A B in e and d. Make
r/y equal to e C; through C andjf draw CJi and it
will be the line required.
Case 2. When the parallel is to be at a given
distance from A B. From any two points, c and
df in the line A B, with a radius equal to the given
distance, describe the arcs e and^.- draw the line
C B to touch those arcs without cutting them, and
it will be parallel to A B, as was required.
Prob. 8. To divide a given line A B into any
proposed number of equal parts.
From A, one end of the line, draw A c, making
any angle with A B ; and from B, the other end,
draw B d, making the angle A B r/ equal to B A c.
In each of these lines A c, B </, beginning at A and
B, set off as many equal parts of any length as A B
is to be divided into. Join the points C 5, 46,
37, &c., and A B will be divided as required.
Prob. 9. To find the centre of a given circle,
that is, of any one already described. Draw any
chord A B, and bisect it with the perpendicular
C D. Bisect C D with the diameter E F, and the
intersection O will be the centre required.
Prob. 10. To draw a tangent to a given circle
that shall pass through a given point, A.
From the centre O, draw the radius OA.
Through the point A, draw D E perpendicular to
O A ; and it will be the tangent required.
Prob. 11. To draw a tangent to a circle, or any
segment of a circle A B C, through a given point
B, without making use of the centre of the circle.
Take any two equal divisions upon the circle
from the given point B, towards d and <?, and draw
the chord e B. Upon B, as a centre with the dis-
366 GEOMETRY.
tance B rf, describe the D.rcfdg\ cutting the chord
eBinJl Make dg equal to dj'; through g draw
g B, and it will be the tangent required.
Pi^ob. 12. Given three points, A, B, C. not in a
straight line, to describe a circle that shall pass
through them.
Bisect the lines A B, B C, by the perpendicu-
lars a b, ba, meeting at d. Upon d, with the dis-
tance ^ A, ^B, or dCi describe ABC, and it will
be the required circle.
P7'ob, 13, To describe the segment of a circle,
of any length A B, and any height C D.
Bisect A B by the perpendicular D^, cutting
A B in c. From c make c D on the perpendicular
equal to C D, Draw A D, and bisect it by a per-
pendicular ejy cutting Dg in g. Upon g the
centre, describe A D B, and it will be the required
segment.
Prob. 14. To describe the segment of a circle
by means of two rulers, to any length A B, and
perpendicular height C D in the middle of A B,
without making use of the centre.
Place the rulers to the height at C j bring the
edges close to A and B ; fix them together at C,
and put another piece across them to keep them
fast. Put in pins at A and B, then move the rulers
round these pins, holding a pencil at the angular
point C, which will describe the segment.
Prob. 15. In any given triangle to inscribe a
circle. Bisect any two angles A and C, with the
lines A D and CDC. From D the point of inter-
section, let fall the perpendicular D E j it will be
the radius of the cii'cle required.
Prob. 16. In a given square, to describe a regu-
lar octagon.
I
GEOMETRY. 367
Draw the diagonals AC and B D, intersecting
at e. Upon the points A, B, C, D, as centres,
with a radius e C, describe the arcs h e /, k e n,
m e g,fe i. Join J n, m h, k /, / «', and it will be the
required octagon.
Prob. 17* In a given circle, to describe any re-
gular polygon.
Divide the circumference into as many parts as
there are sides in the polygon to be drawn, and
join the points of division.
Prob. 18. Upon a given line AB, to construct
an equilateral triangle.
Upon the points A, and B, with a radius equal
to A B, describe arches cutting each other at C.
Draw A C and B C, and ABC will be the triangle
required.
Prob. 19. To make a triangle, whose sides shall
be equal to three given lines, D, E, F, any two of
them being greater than the third.
Draw A B equal to the line D. Upon A, with
the radius F, describe an arc C D. Upon B, with
the radius E, describe another arc intersecting the
former at C. Draw A C and C B, and ABC will
be the triangle required.
Prob. 20. To make a trapezium equal and simi-
lar to a given trapezium A B C D.
Divide the given trapezium ABCD into two
triangles by the diagonal D B. Make E F equal
to A B J upon E F construct the triangle E F PI,
whose sides shall be respectively equal to those of
the triangle A B D by the last problem. Upon
H F, which is equal to D B, construct the triangle
HFG, whose sides are respectively equal to DBC ;
then EFGH will be the trapezium required.
By the help of this problem any plan may be
copied J as every figure, however irregular, may
368 GEOMETRY.
be divided into triangles. Upon this the practice
of land-surveying and making plans of estates is
founded.
Proh. 21. To make a square equal to two given
squares. Make the sides D E and D F of the two
given squares A and B ; from the sides of a right-
angled triangle F D E ; dravv^ the hypothenuse
FE; on it describe the square E F G H, and it
will be the square required.
Proh. 22. Two right lines A B, C D, being
given, to find a third proportional. Make an angle
H E I at pleasure ; from E make E F equal to
A B, and E G equal to CD: join F G. Make
E I equal to E F, and draw H I parallel to F G ;
then E H will be tlie third proportional required ;
that is, EF : EG:: E H: EI, or AB:CD::
C D : E I.
Proh. 23. Three lines being given, to find a
fourth proportional. Make the angle H G I at
pleasure ; from G make G H equal to A B, G I
equal to C D, and join H I. Make G K equal to
E F ; draw K L through K, parallel to H 1 ; then
G L will be the fourth proportional requii'ed ; that
is, G H : G I : : G K : G L, or A B : C D : : E F :
GL.
Proh. 24. To divide a given line A B in the
same proportion as another C D is divided.
Make any angle K H I, and make H I equal to
A B ; then apply the several divisions of C D from
H to K, and join K I. Draw the lines he, if, Ic g\
parallel to I K ; and the line H I will be divided in
e^f, gy as was required.
Proh. 25. Between two given lines A B and C D,
to find a mean proportional.
Draw the right line E G, in which make E F
equal to A B, and F G equal to C D. Bisect E G
gp:ometry. 369
in H, and with H E or H G, as radius, describe
the semicircle E I G. From F draw F I perpen-
dicular to E G, cutting' the circle in I ; and I F
will be the mean proportional required.
Proh. 26. To describe an ellipsis.
If two pins are fixed at the points E and F, a
string put about them, and the ends tied together
at C ; the point C being moved round, keeping
the string stretched, will describe an ellipsis.
The points E and F, where the pins were fixed,
are called theyoa.
The line A B passing through the foci, is called
the transverse axis.
The point G bisecting the tranverse axis, is the
centre of the ellipsis.
The line C D crossing this centre at right-angles
to the tranverse axis, is the conjugate axis.
The latus rectum is a right line passing through
the focus at F, at right angles to the transverse
axis terminated by the curve : this is also called
the parameter.
A diameter is any line passing through the
centre, and terminated by the curve.
A coiyugate diameter to another diameter is a
line drawn through the centre, parallel to a tan-
gent at the extreme of the other diameter, and
terminated by the curve.
A double ordinate is a line drawn through any
diameter parallel to a tangent, at the extreme of
that diameter terminated by the curve.
The transverse axis A B, and conjugate axis
C D, of any ellipsis, being given, to find the two
foci, and from thence to describe the ellipsis.
Take the semi-transverse A E, or E B, and from
C as a centre, describe an arc cutting A B at F
and G ; these are the foci. Fix pins in these
VOL. II. * p B
370 GEOMETRY.
points ; a string being stretched about the points
F, C, G, the elUpsis is described as above.
Prob. 27. The same being given, to describe an
elHpsis by a trammel.
The trammel is an instrument consisting of two
rulers fixed at right-angles to each other, with a
groove in each. A rod with two moveable nuts
works in this groove ; and, by means of a pencil
fixed in the end of the rod, describes the curve.
The operation is as follows :
Let the distance of the first pin at B, from the
pencil at A, be equal to half the shortest axis ; and
the distance of the second pin at C, from A, to
half the longest axis ; the pins being put in the
grooves, move the pencil at A, which will describe
the ellipsis.
Prob. 28. To draw a figure approaching to an
ellipsis with a compass to any length A B, and
width C D.
Draw B P parallel and equal to E C, and bisect
it at 1 ; then draw 1 C and P D, cutting each
other at K j bisect K C by a perpendicular, meet-
ing C D in O J and on O, with the radius O C, de-
scribe the quadrant C G Q.
Through Q and A, draw QG, cutting the qua-
drant at G; then draw G O, cutting A B at M^
make E L equal to E M, also E N equal to E O.
From N, through M and L draw N H and N I;
tlien M, L, N, O, are the four centres by which
the four quarters of the figure are drawn.
It must be observed, that this is not a true el-
lipsis, but only an approximation to it ; for it is
impossible to draw a perfect ellipsis by means of
compasses, which can only describe parts of cir-
cles. The curve of an ellipsis differs essentially
from that of a circle in every part ; and no por-
GEOMETRY. 371
tions of circles put together can ever form an el-
lipsis. But by this means a figure may be drawn,
which approaches nearly to an ellipsis, and, there-
fore, may be often substituted for it when a tram-
mel cannot be had, or when the ellipsis is too
small to be drawn by it. At the joining of the
portions of circles in this operation, the defect is
perceivable ; and the best way is not to join them
quite, and to help the curve by hand.
Prob. 29. An ellipsis, A C D B, being given, to
find the transverse and conjugate axes.
Draw any two parallel lines, A B and C D, cut-
ting the ellipsis at the points A, B, C, D ; bisect
them in e and^ Through e and fy draw G H,
cutting the ellipsis at G and H ; bisect G H at 1 5
and it will give the centre.
Upon I, with any radius, describe a circle, cut^
ting the ellipsis in the four points /^, /, ???, n /join
ky /, and w, n ; bisect k /, or m 7Z, at 0 or p.
Through the points 0, 1, or I, ^, draw Q R, cut-
ting the ellipsis at Q and R ; then Q R will be the
transverse axis. Through I draw T S, parallel to
k /, cutting the ellipsis at T and S ; and T S will
be the conjugate axis.
Prob, 30. To describe an ellipsis similar to a
given one A D B C, to any given length I K, or to
a given width M L.
Let A B and C D be the two axes of the given
ellipsis. Through the points of contact A,D, B, C,
complete the rectangle G E H F ; draw the dia-
gonals E F and G H : they will pass through the
centre at R. Through I and K draw P N and
O Q parallel to C D, cutting the diagonals E F
and GH, at P, N, Q, O. Join PO and N Q,
cutting CD at L and M ; then I K is the trans-.
vei'sCj and M L the conjugate axis of an ellipsis,
p B 2
^7^ GEOMETRY.
that will be similar to the given ellipsis A D B C,
which may be described by some of the foregoing
methods.
Proh. 31. To describe a parabola. If a thread
equal in length to B C, be fixed at C, the end of
a square ABC, and the other end be fixed at F;
and if the side A B of the square be moved along
the line A D ; and if the point E be always kept
close to the edge B C of the square, keeping the
string tight, the point or pin E will describe a
curve E G I H, called a 'parabola.
The Jbcus of the parabola is the fixed point F,
about which the string revolves.
The directrix is the line A D, which the side of
the square moves along.
The axis is the line L K, drawn through the
focus F, perpendicular to the directrix.
The vertex is the point I, where the line L K cuts
the curve.
The latus rectum^ or 'parameter, is the line G H
passing through the focus F, at right-angles to the
axis I K, and terminated by the curve.
The diameter is any line M N, drawn parallel to
the axis I K.
A double ordinate is a right line R S, drawn pa-
rallel to a tangent at M, the extreme of the dia-
meter M N, terminated by the curve.
The abscissa is that part of a diameter contained
between the curve and its ordinate, as M N.
Prob. 32. To describe a 'parabola, by finding
points in the curve ; th,e axis A B, or any diameter
being given, and a double ordinate C D.
Through A draw E F parallel to C D ; through
C and D draw D F and C E parallel to A B, cut-
ting E F at E and F. Divide B C and B D, eacli
into any number of equal parts, as four j likewise
GEOMETRY. S'^S
divide CE and DF into the same number of equal
parts. Through the points 1, 2, 3, &;c. in CD,
draw the Unes 1 a,Q b,o c, kc. parallel to AB; also
througli the points 1, 2, 3, in C E and D F, draw
the lines 1 A, 2 A, 3 A, cutting the parallel lines
at the points <2, bj c; then the points a, b, c, are in
the curve of the parabola.
P?^ob. 33. To describe an hyperbola.
If B and C are two fixed points, and a rule
A B be made moveable about the point B, a
string ADC being tied to the other end of the
ruler, and to the point C ; and if the point A be
moved round the centre B, towards G, the angle
D of the string ADC, by keeping it always tight
and close to the edge of the rule A B, will describe
a curve D H G, called an hyperbola.
If the end of the ruler at B were made moveable
about the point C, the string being tied from the
end of the ruler A to B, and a curve being de-
scribed after the same manner, is called an oppo-
site hyperbola.
The foci are the two points B and C, about
which the ruler and string revolves.
The transverse axis is the line IH, terminated
by the two curves passing through the foci, if con-
tinued.
The centre is the point M, in the middle of the
transverse axis I H.
The conjugate axis is the line N O, passing
through the centre M, and terminated by a circle
from H, whose radius is M C, at N and O.
A diameter is any line V W, drawn through the
centre M, and terminated by the opposite curves.
A conjugate diameter to another, is a line drawn
through the centre, parallel to a tangent with
B B 3
374 PERSPECTIVE.
either of the curves, at the extreme of the other
diameter terminated by the curves.
Abscissa is when any diameter is continued
within the curve, terminated by a double ordinate
and the curve ; then the part within is called the
abscissa.
Double ordinate is a line drawn through any dia-
meter parallel to its conjugate, and terminated by
the curve.
Parameter^ or latus rectum, is a line drawn
through the focus, perpendicular to the transverse
axis, and terminated by the curve.
Prob. 34. To describe an hyperbola by finding
points in the curve, having the diameter or axis
A B, its abscissa B G, and double ordinate D C.
Through G draw E F, parallel to C D ; from C
and D draw C E and D F, parallel to B G, cut-
ting E F in E and F. Divide C B and B D, each
into any number of equal parts, as four ; through
the points of division, 1, 2, 3, draw lines to A.
Likewise divide E C and D F into the same num-
ber of equal parts, viz. four ; from the divisions
on C E and D F, draw lines to G ; a curve being
drawn through the intersections at G, a, Z>, &c.
will be the hyperbola required.
PERSPECTIVE.
Perspective is the art of drawing upon a plane
surface the outlines of objects, so as to give the
same representations to the eye that the objects
themselves do in nature.
This art is of the utmost importance in drawing,
^nd its study cannot be dispensed with by those
PERSPECTIVE. 375
who wish to make any proficiency in this art.
Some knowledge of it ought to be acquired,
previous to the study of every branch of drawing,
whether that of the figure, landscape, flowers, &c.;
for though its utility may not appear equally evi-
dent in all these, yet there are many cases in each,
where it is of indispensable necessity ; and an ac-
quaintance with it will save the student the trouble
of much wrong thinking, and will enable him to
avoid many errors which he otherwise must neces-
sarily fall into.
It is true, that many people learn to draw without
studying perspective, and too many of those whose
profession it is to teach this useful branch of edu-
cation, do not sufiiciently recommend to their
pupils to learn the principles of this science. The
reason of this it is not difficult to point out. The
study of perspective, like that of geometry, has in
itself but few charms, and it is only by being well
convinced, that without it we can never hope to
arrive at excellence, and by experiencing how
much it accelerates and assists us in our practice
of drawing, that we can with patience and resolu-
tion go through studies that certainly appear to
most people dry and unentertaining. Unfortu-
nately, from this circumstance, and from the ab-
struse and obscure manner in which it is treated
off by the generality of writers on the subject, few
will take the trouble of making themselves ac-
quainted with a science so necessary.
But though the understanding perspective
thoroughly^ certainly does require considerable
geometrical knowledge, added to great patience
and persevering investigation, yet so much as would
enable those who draw to avoid making any very
B B 4
376 PERSPECTIVE.
glaring blunders, and render their study of drawing
much more pleasant and easy, is so far from being
difficult, that it is astonishing any one should hesi-
tate a moment about acquiring it.
Some part of the blame may, however, be fairly
laid to the want of a treatise on perspective, of
an easy and popular kind, such as might suit those
who have had no opportunities of acquiring a
knowledge of geometr3\ It would be in vain to
endeavour to supply this deficiency properly in a
work of so limited a nature, and which embraces
so many subjects as the present; yet though our
/, plan will not permit us to treat of it so fully as it
deserves, we shall lay down, as concisely as pos-
sible, a few of its principal rules, the understand-
ing of which will be found useful to beginners in
the art of draw ing.
Exjjlanatio}! of the piincipal Terms used in
Perspective.
The perspective plane is the surface of the pic-
ture itselfi which may be imagined to be a plane of
glass placed upright between the spectator and
the objects to be drawn. Then, if lines or rays be
supposed to come from every part of the objects to
the spectator's eye, when viewing them through
the glass, they would cut the plane in certain
points ; and if these points were connected by
lines, they would give the perspective represent-
ation. It is upon this simple idea that all the
rules of perspective are founded : they are so
many methods of finding out the above-mentioned
points ; and when the light, shadow, and colour,
are added, the whole constitutes a picture exactly
resembling the original.
I
PERSrECTIVE. 377
Visual raifs are the rays of light which come
from the different parts of the objects to our eyes.
Point of sight is the spectator's eye. This has
been erroneously confounded with the centime of
the picture, as will be seen afterw^ards.
What is called an original line, is any line in
Nature, or in the objects themselves, which are to
be drawn in perspective.
An original plane is any surface or plane of the
objects to be represented.
If we suppose a line to proceed from the eye,
parallel to any line in the objects we are viewing,
and to continue till it arrive at the picture or
perspective plane, the point where it would touch
the plane is called the vanishing jJoint of the line.
All lines that are in Nature parallel to each
other have the same vanishing points. The reason
of this will be easily seen, if the reader considers
the method of finding the vanishing point of an
original line just mentioned; for the same line
which would find the vanishing point of one, will
do for them all, and form only one point.
If we could suppose a plane or surface to pro-
ceed from the eye of the spectator, in a direction
parallel to any side of an object which we view
through the plane of glass, and if it continue till
it arrive at the glass, the line which it would form
by contact with the glass, is called a vanishing line ;
and it is the vanishing line of the side of the
object which the supposed plane was parallel to.
In every p)icture or perspective plane, there is a
point, where a line drawn from the eye perpen-
dicular to the picture, would touch it ; this point
is called the centre of the picture, and is the same
which is often called in old books on perspective,
the jioii'i'l of sight. But this is a wrong term tor it;
.37(^ PERSPECTIVE.
the |)oint of sight, strictly speaking, being in tlie
sj)ectator's eye, and consequently, not any point in
tlie picture. Although, from its name, we should
expect to find it always in the middle of the repre-
sentation, yet this is by no m.eans the case, for
sometimes it is near one of the sides, particularly in
what is called parallel perspective ; though gene-
i-ally in obhque perspective, it is in the middle of
the picture. And here it should be observed, that,
strictly and properly, it should always be in the
middle of the picture, when circumstances of con-
venience will admit of it ; for it is that point which
the spectator is supposed to look full against, or
which is exactly opposite to his eye when he views
a picture, and surely the best way to see a picture,
is to look directly against the middle of it. How-
ever, in many kinds of perspective drawings, it is
not convenient, on account of room, to have this
point in the middle, as may easily be imagined by
considering Plate 6. Fig. 1., where G is the centre
of the picture.
It will be easily conceived, from the description
of vanishing points, and the centre of the picture,
that this last must be the vanishing point of all lines
that are in Nature perpendicular to the picture.
If a plane be supposed to proceed from the eye,
as before, parallel to the floor or level ground till
it arrives at the picture, the line where it meets it
is called the vanishing line of the horizon, or hori-
zontal line. This line is of great importance in
perspective : the centre of the picture is always
somewhere in this line. Its height is necessarily
regulated by the height of the eye from the
ground ; in landscapes, and views of places, it is
generally kept one-third of the height of the pic-
ture froin the bottom, though thib yv\\^ i.s not
PERSPECTIVE. 379
always adiiered to ; for when we stand upon high
ground, the horizontal hne rises in proportion.
Suppose the view to be taken on level ground, the
head of a man represented standing on the ground,
would come to this line, and that whether the
man be near or far off; that is, wherever his feet
are, his head must always come to the horizontal
line, if he be standing upright on the ground.
Distance of the picture means the supposed dis-
tance of the eye from the centre of the perspective
plane or picture.
This distance may be chosen at pleasure ; but
a judicious choice of it is very important, for the
variation of this distance affects every perspective
representation, so as to render them either pleasing
or distorted. Long distances, in general, give the
best representation ; but they are not always con-
venient, or to be attained. Experience alone can
direct a proper medium.
Parallel pei^spective is where the picture is sup-
posed to be so situated, as to be parallel to the
side of the principal object in the picture, as a
building, for instance. Then the lines on those
sides of the building that are parallel to each other
continue parallel on the picture, and do not vanish
into any point ; while the lines at right angles to
the former vanish into the centre of the picture.
This will be exemplified in Plate 6. Fig. 1.
The picture being supposed to stand parallel to
the side of the house A B C D, the lines A B, DC,
which in Nature are parallel to each other, must
be made parallel in the perspective representation.
But the lines BE, CF, which in Nature are at
right angles to A B, and D C, and, consequently,
also to the picture, tend towards a point ; and this
380 PERSPECTIVE.
point G, lowiirds which they tend, is the centre of
tlie picture.
Oblique persjJective is when the plane of the pic-
ture is supposed to stand oblique to the sides of
the objects represented ; in which case the repre-
sentations of the Hues upon those sides will not be
parallel among tliemselves, but will tend towards
their vanishing point. This kind of perspective is
show^n in Plate 7* Fig. 1.
A hird^s-eye view is a view supposed to be taken
in the air, looking down upon the object; and
differs from the usual way of drawing perspective
views, only in supposing the horizontal line to be
raised much higher.
When an object is to be drawn in perspective,
all its parts must be measured, so that we may be
able to lay them down from a scale of equal parts.
Having determined whether it is to be parallel
or oblique perspective, the first thing to be drawai
is the horizontal line, which is to be put parallel to
the bottom of the drawing, and as high above it
as the height of a man's head, as H G, Plate 6.
Fig. 1., which is five feet six inches above the bot-
tom of the house. Next determine on the centre
of the picture G, which must be placed so as to
leave convenient room for the representation. Fix
on C the nearest corner of the object, and draw the
perpendicular C B : lay off C D equal to the length
of the building, and draw D A and A B. From C,
tlie nearest corner, draw C G, to the centre of the
picture. C G now contains the line which repre-
sents the bottom of the end of the house ; but this
is an indefinite representation, of which we do not
yet know the exact length. The method of deter-
mining this is as follows : Continue the lineDCtoI,
PERSPECTIVE. 381
and make C I equal to the width of the house.
From G, the centre of the picture, lay off G K
equal to the distance of the picture, the choosing
of which must be regulated by taste. Draw I K,
cutting C G in F ; then is C F the exact width of
tlie house in perspective, which was equal to C I.
To find the middle of this end of the house, you
cannot divide it by your compasses, because the
farthest half will appear less than the nearer ; but
if you divide C I into two equal parts in L, and
draw L K, it will cut C F into two equal parts per-
spectively. Or it may be found more simply thus :
Ilaving drawn the lines B E and C F to the centre
of the picture, draw the diagonals E C, B F cross-
ing each other in M, and raise the perpendicular
M N, which is in the middle of the gable-end.
To find the height of the gable, lay its actual
height above B E, upon the corner line B C con-
tinued, as B O, and draw O G ; this crossing the
perpendicular M N, gives N the point of the gable.
The top of the chimney must be drawn in the same
manner, by laying its real height, taken from a
scale on OP, and drawing P G, lay off L m and
L72, each equal to half the width, and draw from
these points to the distance point k ; this will cut
the bottom of the house C F, in the points o andp ;
from these draw perpendiculars, which will give
the perspective width of the chimney. To obtain its
thickness, lay off P Q equal to its thickness, and
draw Q (t ; then drawing from a the line a b, you
obtain the exact width of the chimney. From b
draw b c, and from d draw d c. The other end of
the gable may be drawn by two different methods.
The first is by supposing the front of the house
transparent, and drawing the other end as if seen
through it, in the same manner as the end we have
382 PERSPECTIVE.
described, by laying its width from D to R, and
drawing to the distance-point K. By raising the
perpendicular in the middle, you will meet the
ridge-line from the other gable in d. The other
method is as follows : Through the centre of the
picture G draw the line S T, upwards, and down-
wards, and perpendicular to the horizontal line.
Then continue the line of the roof B d till it meet
S T in S. From A draw A S, which will give the
other gable, and S will be the vanishing point for
all hues parallel to B rf and Ad; if N E be conti-
nued in like manner, it will give T for its vanish-
ing point. The doors and windows on the side
A B C D are laid down from a scale, because that
side, being parallel to the picture, does not vary
from its geometrical delineation, except shewing
the thickness of the reveals, or edges of the doors
and windows. If there had been any windows in
the side B E F C, they would be drawn in perspec-
tive by the same method that was used for finding
the width of the house and the middle of the end ;
viz. by laying off the actual dimensions from C upon
CI, and drawing from these points to the distance-
point K, which would transfer these divisions to
the bottom of the house CF, and then perpendicu-
lars might be drawn upwards.
This practice is farther explained by the follow-
ing rule.
To divide a line in perspective which is parallel
to the horizon, and which tends to a vanishing-
point, into any number of equal parts; or to divide
it in any required proportion.
Let A B be the line going to its vanishing-point
C (Fig 2.); and first let it be required to divide
that line into six equal parts. Let C D be the hori-
zontal line, and AE the ground-line drawn parallel
10
PERSPECTIVE. 388
to it. Lay ofF, at pleasure, CD for the distance of
the picture, if C be the centre of the picture.
Draw a line from D, touching the end B of the line
to be divided: draw DBE, cutting the ground-
line in £. Then AE represents the actual dimen-
sions of the line AB, wliich is seen in perspective.
(Here it may be observed, that this gives a rule
also for finding the real length of any line which
tends to a vanishing-point.) Divide AE into the
same number of equal parts into which you pro-
posed to divide the given line AB; as Al, 12, 23,
&c. Then from these different divisions draw lines
to D, cutting the line AB in «, Z>, c, dy &c., which
will represent the required number of equal parts,
but diminishing in size as they are farther removed
from the eye. If it be wished to divide the line
AB into any number of unequal parts, or to lay off
doors, windows, &c. upon it, the line AE, found as
before, must be divided in the required proportion ;
and lines drawn from those to D will give the re-
quired divisions on AB, from which perpendiculars
may be drawn for the doors, windows, he.
To draw a circle in perspective.
The perspective representation of every circle is
a regular ellipsis, when the eye is without the
circle, which may be demonstrated, by considering
that the rays from the circumference of the circle
to the eyCj form an oblique cone. But it is well
known to those who are acquainted with conic sec-
tions, that every section of a cone, whether right
or oblique is a true ellipsis, except in one case only,
which is, when the section is taken sub-contrary to
its base, a situation which happens so rarely in
drawings, that it may be disregarded altogether,
and the section of a cone, or the perspective of a
circle, in all cases considered as a perfect ellipsis.
rERSPECTIVE.
The most correct and easy method of drawing an
ellipsis is to find the transverse and conjugate
axes, and then to complete the curve by a trammel,
or by hand. But as it is very difficult to find the
transverse and conjugate axes of the ellipses which
are the perspective representations of circles, re-
course is generally had to anotlier method of
obtaining the curve. The circle is circumscribed
by a square, as K L M N, in Fig. 3., and the dia-
gonals and the lines across the centre, and paral-
lel to the sides, are drawn; also the lines, c/,
cdy are drawn parallel to the sides, through the
points v;here the circle is cut by tlie diagonals.
This square, with all these lines drawn across it, is
now put in perspective as follows : Draw A B for
the horizontal line, and fix B for the centre of the
picture, and A B for the distance of the picture.
Make D C equal to the width of the square, and
draw C B, DB ; draw C A to the distance-point A,
cutting ofFDG equal to the depth of the square;
then draw G F, parallel to D C, which completes
the perspective of the square ; also draw the diago-
nal DF. Take now the distances M^/, cN; and
transfer them to D .z-, o C ; from these points x and
0 draw lines to the vanishing point B, cutting the
diagonals of the square. The points in this reticu-
lated square in perspective, which correspond to
those in the square KLMN, where the circle
passes through, must now be observed, and a curve
traced through them with a steady hand : it will
be the perspective required. Even in this process,
it is of considerable use to know that the curve you
are tracing is a regular ellipsis ; for though you can-
not easily ascertain the axes exactly, yet you may
^ery nearly ; and the eye very soon discovers
whether the curve which has been drawn, be that
of a regular elhpsis or not.
PERSPECTIVE. 3S5
Upon the same principle the row of arches
(Fig. 4.) is drawn. The width of the arches and
piers is obtained in the same manner as Avas shown
in Fig. 2. ; viz. by laying their dimensions upon the
ground-line A B, and drawing lines to the dis-
tance-point. The curves of the arches are then
found, by drawing the lines which correspond to
those in half the square, Fig. 3., in the same man-
ner as described above for the circle.
Fig. 5. shows the appearance of circles drawn upon
a cylinder, when H I is the horizontal line. The
circle drawn on the cylinder at that place is seen
exactly edgeways, and appears only as a straight
line; that next above it is seen a little under-
neath; the next still more; and so on, as they
rise higher, appearing like so many ellipses of the
same transverse diameter, but whose conjugate
diameters continually increase in length as they
rise above the horizontal line. On the contrary,
you see the under sides of the circles drawn below
the horizontal lines; but they observe the same
law, being so many ellipses whose conjugate dia-
meters vary in the same proportion. A little re-
flection on this simple example will enable those
who draw to avoid many ridiculous mistakes which
are sometimes committed, such as showing the two
ends of a cask, or the top and bottom of a cylinder,
at the same time.
PI. 7. Fig. 1. shows the method of drawing a
building, or other object, in oblique perspective.
A B is the horizontal line, and C D the ground-line
parallel to it as before. Here neither of the sides
of the house is parallel to the picture, but each
goes to its respective vanishing point. Having
fixed on the nearest corner E, draw EB, at plea-
sure, for one side, and choose any point F for the
VOL. II. c c
386
PERSPECTIVE.
centre of the picture; tlieii, to find the other side,
lay off' F G equal to the distance of tlie picture,
which, as before, depends upon taste only; draw
B G and G A perpendicidar to B G, cutting the
horizontal line in A, the other vanishing point.
Draw now E A for the other side. To cut off" the
several widths of the two sides of the house, which
as yet are only drawn to an indefinite extent, two
distance-points must be laid down, viz. one for each
vanishing point. To do this, extend the compass
from B to G, and lay the distance taken in it fiom
B to H, which will give H for the distance-point of
B, and which is to cut off all the divisions on the
side E B. Also extend the compasses fi'om A G,.
.^nd lay down A I. I is the distance-point of A,
and is used for transferring all divisions upon the
side E A, from the ground-line C E, These points^
and lines being adjusted, the process is not much
different from parallel perspective ; only here, equal
divisions on each side of the building, as doors, win-
dows, diminish as they recede, in the same way as
on the side B E F C, PI. 6. Fig. 1. Take the real
length of the side E L, from the same scale used for
laying down the horizontal line, and lay it down on
the ground-line from E to C, and draw^ C I, cutting
off E L for the perspective length of the building.
For the other side of the house, lay its widtli down
in the same manner, from E to D, and draw D H,
cutting off E N for the perspective width. Raise
the perpendiculars EM, L K, and N O, for the
three angles of the house. Lay the height of the
building upon the corner that comes to the ground-
line, as E M, and draw MK and M O to their several
vanishing points. Also lay all the heights of the
doors and windows, and other divisons, upon E M,
and draw them to the vanishing points A and B.
PERSPECTIVE. 387
To lay down the widths of the doors and windows,
put their actual widths upon C E, and draw from
them to the distance-point I, which cuts off all
divisions upon the side L E, and then raise the per-
pendiculars. The gable-end is found exactly in
the same manner as was described in PI. 6. only
taking care to use the proper distance-point H.
The manner of finding the width of the chimney is
different. Lay off b a for the height of the chimney
above the top of the gable, and draw a c parallel to
the horizontal line ; then put a c equal to the actual
thickness of the chimney, and draw a d to the
vanishing point A ; draw also c d to the distance-
point I, cutting oW admd : then having drawn ef
from the nearest corner of the chimney, which
was found as in PI. 6. Fig. 1. Draw df to the
vanishing point B, cutting o^ efi'oi' the exact per-
spective width.
Fig. 2. represents the method of finding the per-
spective of a circle in oblique perspective. A B is
the horizontal line, C the centre of the picture, and
D, E, the distance-points. The process is exactly
the same as that just described, the several divi-
sions of the reticulated square in PI. 6. Fig. 3.
being laid upon the ground-line FG, and from these
lines are drawn to the distance-points. The per-
spective of the square is then drawn with all the
lines across it, and the curve traced through the
different points.
By drawing these examples frequently over, to
large scale, and reflecting upon them with atten-
tion, the student will become familiar with their
use J and as they include the cases which most fre-
quently occur, he will find great benefit from the
knowledge of them.
c c 2
38S-
Dtaumg the Figure.
The study of the human figure has always been
considered by artists as the most important part of
the art. It is the most difficult, and is by many
considered as contributing the most of any to
general improvement ; though there are some who
carry this idea to too great an extent, saying, tliat
a person who can draw the human figure well can
draw every thing besides. But this, it is well
known, is not the case ; there being many artists
who can draw the figure very well who cannot
draw landscape nor architecture. To draw any
thing well requires a particular study. The study
of the figure, however, includes all the finest prin-
ciples of the art ; and when the eye of the student
has been accustomed to copy faithfidly all the mi-
nute circumstances which constitute the character
©f a figure, and to attend to the innumerable beau-
ties and graceful forms which it presents, he will
be better qualified to pursue with advantage every
other branch of the fine arts.
In learning to draw the human figure, it is ne-
cessary to begin with eacli of the parts separately,
and after sufficient practice in that way, to proceed
to put them together in the complete figure.
The head being the most important part of the
human body, it should be studied first. For this
purpose, the student should copy the best drawings
he can procure of the eye^ mouthy nose, and ear,
separately and on a large scale j and of these, a
front view, profile or side view, oblique view, &c.
The best materials for drawing these, as well as
all other parts of the figure, is black chalk, or black
lead ; the former may be used either upon white
DRAWING THE FIGURE. 389
paper, or upon middle-tint paper ; and in that case,
white chalk may be used for laying on the lights.
Black lead is only used upon white paper. A
piece of soft charcoal may be made use of for first
slightly sketching in the general form, which must
afterwards be gone over and corrected with the
black chalk. The false lines of the black lead may
be removed by the Indian rubber ; but we would
recommend to be as sparing as possible of this, as it
is more improving to endeavour to draw every
thing correct and decided at once, and not trust
to the being able to erase the lines which are
wrong.
The shadows may be laid on by drawing parallel
curve lines, according to the situation of the part,
crossing them occasionally, and softening them in
with more delicate lines, where necessar}^
All the parts of a human figure are composed of
curved surfaces : no straight lines are ever admis-
sible ; but every line should have a graceful turn ;
and it is this circumstance particularly that occa-
sions the study of the figure to give so much
freedom in drawing.
Care should be taken, that no lines ever cross
each other at right angles, which gives a disagree-
able net-like appearance ; neither should the cross-
ings be too oblique, as then they are confused : a
proper medium will be acquired by the study of
good drawings or prints j in general, however,
crossing should be avoided as much as possible.
Sometimes the shadows are rubbed in, or their
edges are softened with a stump, which is a very
expeditious way, and produces a fine effect ; but it
should be used with discretion, as it is better to
execute the shadows in a clear and regular manner
by soft lines.
c c 3
390 DRAWING THE FIGURE.
Care should be taken not to make the hnes harsh
and hard, Hke those of an engraving; they should
be softer and more mellow. On this account,
draxvings are much better to learn from than
prints ; as, by copying the latter, the student is
very apt to acquire a dry and hard manner.
But we particularly caution him to avoid copy-
ing with a pen all the lines in engravings used for
the shadows, which some, who have not been ac-
customed to see good drawings, are apt to do.
Many productions of this kind have been exe-
cuted with an immensity of labour, and have been
thought very fine by those who had but little
knowledge of the art ; yet artists, and those who
are good judges, always lament to see so much
patience and labour misapplied.
In copper-plate engravings, shadows are gene-
rally produced by lines : but this arises from the
nature of the process ; and in drawing, which is of
a very different nature, there is not the same ne-
cessity for them. In general it should be ob-
served, that the less labour there appears in any
drawing the better ; and that though every possi-
ble pains should be taken to make drawings or
paintings excellent, yet this labour should be al-
ways disguised as much as possible, and the whole
should appear as if executed with the greatest ease.
*' In learning to draw, it is of more importance
than is generally supposed, to copy from the
finest works only. The most prejudicial quality
of a model is mediocrity. The bad strike and dis-
gust ; but those that are not good, nor absolutely
bad, deceive us by offering a dangerous facility.
It is for this reason that engraving contributes to
the progress of the arts, when it is employed on
subjects that are judiciously chosen ; but is too
DRAWING THE FIGURE. 391
often preJLidiciul, by the iiidiiieient works it multi-
plies without number. But let Raphael be copied
by skilful engravers, let a young artist profit by
his labours, and works without dignity and ex-
pression will soon become intolerable to him ; he
will perceive to wiiat an elevation tlie excellence
of the art can raise him.
<' The way to avoid mediocrity, is by the study
and imitation of beautiful productions ; or, in
want of them, of the most finished translations that
have been made from them ; for so we may call
beautiful prints. Let a young draughtsman study
the heads of Raphael, and he will not see without
disgust the soi'did figures of indifferent painters.
But if you feed him with insipid substances, he
will soon lose the taste necessary to relish great
excellencies. In the one case he will advance
firmly in his career : in the other he will conti-
nually totter, and even not be sensible of his own
weakness."
Having copied frequently the parts of a face, he
is next to proceed to the entire head ; drawing
first a front view, then a profile, a three-quarter,
and so on ; varying it in every possible direction,
till he is thoroughly acquainted with the appear-
ance of all the principal lines in every situation.
In making these studies, he should be contented at
first with drawing mere otitlhies, as they are by far
of the most importance ; and it should be remem-
bered in general, that to make a good outline is
always the most desirable attainment.
The student should now accompany his lessons
by making observations on good casts and living
models; but more particularly the former, as indi-
vidual nature is seldom fine, and there is danger of
c c 4
392 DRAWING THE FIGURE.
copying what is bad, and acquiring false ideas of
beauty.
By these exercises he will have acquired some
facility in handhng his pencil, and he will be thus
prepared for the study of the whole figure. But
before he can proceed to this with advantage,
we would recommend to him the study of
anatomy.
An artist who is not acquainted with the form
and construction of the several bones which sup-
port and govern the human frame, and does not
know in what manner the muscles moving those
bones are fixed to them, can make nothing of
what appears of them through the integuments
with which they are covered ; and which appear-
ance is, however, the noblest object of the pencil.
It is impossible for an artist to copy faithfully
what he sees, unless he thoroughly understands it.
Let him employ ever so much time and study in
the attempt, it cannot but be attended with many
and great mistakes ; just as it must happen to a
man who undertakes to copy something in a lan-
guage which he does not understand, or to trans-
late into his own what has been written in another,
on a subject with which he is not acquainted.
But it is not necessary for him to study anatomy
as a surgeon, nor to make himself acquainted with
all the nerves, veins, &c. It is sufficient to study
the skeleton, and the muscles which cover them,
and of these, he should most particularly make
himself familiar with those muscles which most
frequently appear and come into action.
For this purpose, he should procure plaster casts
of the anatomy of the human body, and consult
treatises written upon the subject; and if he have
19
DRAWING THE FIGURE. 303
opportunity, it will be proper afterwards to attend
discussions and lectures on anatomy.
He should also use every possible opportunity of
making; observations on the actions of the muscles
in nature.
Being thus thoroughly prepared, he will be en-
abled to draw the human figure with great advan-
tage, and he will make a more rapid progress than
he could have done without these previous studies.
Symmetry y or proportion^ will be best learned by
copying after the antique statues, of which plaster
casts may be easily procured. Nature, whicli in
the formation of every species seems to have aimed
at the last degree of perfection, does not appear to
have been equally solicitous in the production of
individuals. Parts of individuals are frequently as
beautiful as possible, but a complete whole is never
to be met with.
The practice of the ancient Greek statuaries
was to select from various individuals tlie most
beautiful parts, and by combining them to pro-
duce figures more perfectly beautiful than nature
ever presented.
Till the student has thus imbibed a proper I'elish
for beautiful proportions, and been well grounded
in their principles, he should not proceed to draw
from living models.
In drawing from plaster casts, a good deal de-
pends upon choosing a proper view, and placing the
model properly with regard to the light, which
should always come in obliquely from above, as it
generally does in the daytime. If a candle be used,
it should be so high as to cast the light downwards
upon the model. The light should only come
from one part, as cross lights will distract and
spoil the shadows.
o94 DRAWING THE FIGURE.
After the student has with indefatigable labour
and persevering zeal gone through all these studies,
and acquired a facility of drawing the human figure
in every possible situation, and under every variety
of form and circumstance, a great deal remains for
him still to do, before he can be considered as an
artist. He has as yet conquered only the mechani-
cal difficulties; but his mind must be cultivated,
and he has all the higher and more refined parts of
his art to study.
It is the business and duty of the naturalist and
historian to draw objects as they find them, and
represent them with all those imperfections and
blemishes to which, as individuals, they are sub-
ject. But an ideal painter, and such alone is a true
painter, resembles tlie poet; his creative fancy
soars above common nature, and he represents
objects endued with all that perfection which
belongs to the species, but which is rarely found in
the individual.
A good choice of subjects for the exercise of his
pencil is now to be considered. For this purpose,
he should enrich his mind wdtli a great variety of
knowledge : historians and poets should be his con-
stant companions ; and he should make himself
acquainted with the customs and manners of an-
cient as well as modern nations.
His invention should, now be continually exer-
cised, and free scope should be given to the wildest
sallies of his imagination, which, however, should
never exceed the bounds of probability.
*' It is indisputably evident," says Sir J. Rey-
nolds, " that a great part of every man's life must
be employed in collecting materials for the exer-
cise of genius. Invention, strictly speaking, is
little more than a new combination of those images
DRAWING THE FIGURE. 395
which have been previously gathered and deposited
in the memory. Nothing can come of nothing ;
he who has laid up no materials, can produce no
combination.
" He should study the works of former artists,
learn what subjects they have painted, and liow
they have treated them. A student unacquainted
with the attempts of former adventurers, is always
apt to over-rate his own abilities, to mistake the
most trifling excursions for discoveries of moment,
and every coast new to him, for a newly-discovered
country.
" On whom, however, can he rely, or wlio shall
show him the path that leads to excellence ? The
answer is obvious : those great masters who have
travelled the same road with success are the most
likely to conduct others. The works of those who
have stood the test of ages, have a claim to that
respect and veneration to which no modern can
pretend. The duration and stability of their fame
is sufficient to evince that it has not been sus-
pended upon the slender thread of fashion and
caprice, but bound to the human heart by every
tie of sympathetic approbation.
*' But though these masters should be studied,
they should not be servilely followed. The stu-
dent, instead of treading in their footsteps, should
only keep the same road. He should endeavour
to invent on their principles and way of thinking j
he should possess himself with their spirit ; he
should consider how they would treat his subject,
and should work himself into a belief that they are
to see and criticise his picture when completed.
Every attempt of this kind will rouse his powers."
Whenever a story is related, every man forms a
picture in his mind of the action and the expression
396 DRAWING THE FIGURE.
of the persons employed. The power of repre-
senting this mental picture on canvass is what we
call invention in a painter.
In the conception of this ideal picture, all the
little circumstances should be contrived in such a
manner, that they shall strike the sp^ectator no
more than they did himself in his conception
of the story. Thus there must be a principal
object, which should receive the principal mass
of light ; and though a second and third group
may be added, and a second and third m^ass of
light, yet they should be all kept so subordinate^
that they do not come in competition with the
principal.
In the design or composition of a picture, sini'
plicity is of the first importance. The story should
be distinctly told, and nothing should be introduced
but what is absolutely necessary.
Among the most difficult and important of the
higher branches of the art, is the expressions of the
passions.
It is not enough for a painter to delineate the
most exquisite forms, give them the most graceful
attitudes, and compose them well together ; he
must express by their actions and countenances the
state of their minds ; they must appear to feel and
to think.
Many have written, and among the rest the
famous Le Brun, on the various changes that,
according to various passions, happen in the muscles
of the face. They observe, for example, that in
fits of anger, the face reddens, the muscles of the
lips puff out, the eyes sparkle ; and that, on the
contrary, in fits of melancholy, the eyes grow mo-
tionless and dead, the face pale, and the lips sink
in. It may be of service to a painter to read them
DRAWING THE FIGURE. 397
and such other remarks ; but it will be of infinitely
more service to study them in nature itself, from
which they have been borrowed, and who exhibits
them in that lively manner which neither tongue
nor pen can express.
The colouring must be regulated by the same
general principles as the composition. Gaudiness
and glare ought to be studiously avoided, and a
quietness and simplicity should reign through the
whole work. In landscapes, distinct and unbroken
colours, such as green, red, &c. are seldom or ever
admissible ; the tints should be always varied and
broken. But in historical subjects frequently, dis-
tinct colours are employed, but they must be
placed with respect to each other, so that the effect
of the whole be hajmonious.
The art of disposing the drapery makes a very
considerable part of the painter's study. To make it
merely natural is a mechanical operation, to which
neither genius nor taste are required; whereas,,
it requires the nicest judgment to dispose the dra-
pery, so that the folds have an easy communication^
and gracefully follow each other with such natural
negligence, as to look like the effect of chance, and
at the same time show the figure under it to the
utmost advantage.
In the higher style of painting, the difference in
the materials of which the drapery is composed,,
that is, whether it is silk, linen, woollen, &c. is
never remarked ; it is simply drapery, and nothing
more.
We have now tre ated, as fully as our limits will
permit, of the various excellencies necessary to be
acquired by an artist. It will be easily perceived,
that to accomplish all these objects is by no means
an easy task.
S9S I>RAWING THE FIGURE.
In some, an inclination to pursue the arts
appears at a very early period of life, and it is often
difficult to ascertain the circumstance which gave
that particular impulse to the mind ; though there
must always be some accidental circumstance, not
depending upon ourselves, that creates in us that
desire.
When a boy is possessed of good talents, and
has so strong a passion for the arts, that scarcely
any thing can restrain him, there can be little fear
of his doing well, if suffered to follow the bent of
his inclination ; but without this, nothing should
induce him to engage in a profession of so arduous
a nature, and which requires such unwearied appli-
cation. He may learn to draw the correct outlines
of buildings, and other regular objects, by the rules
of perspective ; but the forming fine pictures, so as
to affect the mind, is an art not reducible to rule 5
and though much may be taught, yet much more
will ever depend upon the mind of the artist. Here it
is that the existence of a quality which distin-
guishes one man from another is so obvious.
This has been denominated by various appellations,,
none of which are capable of being correctly de-
fined. It has been called genius^ tastCy souly mind,
and a variety of other teims, all of which are inde-
finite, and prove that we know but little of our
own nature.
It will be foreign to our purpose to enter into any
discussion on this subject; but we shall add a pas-
sage relating to it from the lectures of the late Sir
Joshua Reynolds : " There is one precept," he
observes, *' in which I shall be opposed only by
the vain, the ignorant, and the idle. I am not
afraid that I shall repeat it too often. You must
have no dependence on your cAvn genius. If you
DRAWIVG THE FIGURE. 399
have great talents industry will improve them : if
you have moderate abilities, industry will supply
their deficiency. Nothing is denied to well-directed
labour; nothing is to be obtained without it. Not
to enter into metaphysical discussions on the nature
or essence of genius, I will venture to assert, that
assiduity unabated by difficulties, and a disposition
eagerly directed to the object of its pursuit, will
produce effects similar to those which some call
the result of natural pouters. Though a man can-
not at all times, and in all places, paint or draw,
yet the mind can prepare itself by laying in proper
materials, at all times and in all places."
" I cannot help imagining that I see a promis-
ing young painter, equally vigilant, whether at
home or abroad, in the streets or in the fields.
Every object that presents itself is to him a lesson.
He regards all nature with a view to his profession,
and combines her beauties, or corrects her defects.
He examines the countenances of men under the
influence of passion, and often catches the most
pleasing hints from subjects of turbulence or de-
formity. Even bad pictures themselves supply
him with useful documents ; and, as Leonardo da
Vinci has observed, he improves upon the fanciful
images that are sometimes seen in the fire, or are
accidently sketched upon a discoloured wall."
"The artist who has his mind thus filled with
ideas, and his hand made expert by practice, works
with ease and readiness; whilst he who would
have you believe that he is waiting for the inspir-
ations of genius, is in reality at a loss how to begin,
and is at last delivered of his monsters with diffi-
culty and pain."
" What then," exclaims Gesner, " must be the
fate of those who do not join an inflexible labour
400 DRAWING LANDSCAPES.
fo an habitual meditation? Let the artist who
despises or neglects these important means make
no pretension to the recompense due to active and
sensible minds. There is no reputation for him,
to whom a taste for his art does not become his
ruling passion ; to whom the hours he employs in
its cultivation are not the most delicious of his
life ; to whom the study of it does not constitute
his real existence and his primary happiness ; to
whom the society of artists is not, of all others, the
most pleasing ; to him whose watchings, or dreams
in the night, are not occupied with the ideas of his
art ; who in the morning does not fly with fresli
transport to liis painting-room. But, of all others,
luihappy is he who descends to flatter the corrupt
taste of the age in whicli he lives, w^ho delights
himself with applauded trifles, who does not labour
for true glory, and the admiration of posterity.
Never will he be admired by it ; liis name will
never be repeated ; his works will never fire tlie
imagination, nor touch the hearts of those fortun-
ate mortals who cherish the arts, who honour their
favourites, and search after their works.'*
The Drawing of Landscapes.
Every one who wishes to learn to draw land-
scapes should begin by the study of perspective.
This will enable him not only to understand and
draw all the parts of buildings which so frequently
form a principal feature in views of places, but
will also give him true ideas of the method of ex-
pressing distances, the winding of roads, and a
variety of particulars that are continually occurring.
Having made himself master of the principal
difficulties in perspective, he should next copy
DRAWING LANDSCAPES. 401
some good drawings ; and here it is of great im-
portance that what he copies first, shoidd be veinj
excellent ; for it is an absurd notion, that indiffer-
ent drawings will do to begin with, or to bring the
hand in, as it is termed j but, it has been justly ob-
served, the most likely effect these can produce
will be to put the hand out.
In choosing drawings to copy for beginners,
particular attention should be paid to select those
where the outlines or forms of the objects are dis-
tinctly and correctly drawn, and not those in
which a ^ood effect only has been principally aimed
at. The first thing to be studied, is to be able to
express with the black-lead pencil, decidedly and
truly, the forms of all sorts of objects ; and till this
is attained, no attempt should be made at finished
drawings or pictures.
Black-lead is the most useful material for draw-
ing the outlines of landscapes, which are best
executed with this alone, and should not be gone
over afterwards by the pen, which, except it be
very judiciously managed, generally gives an ap-
pearance of hardness.
Indian ink alone should be used for the shadows
till the student has advanced very considerably ;
nor till then should colours of any kind be used.
Beginners are always desirous of producing pictures
and making coloured drawings ; but nothing is more
hurtful than the practising this too early. The first
thing to be learned, is to draw forms correctly; next,
the mode of shadowing objects truly ; then the ge-
neral light and shadow of a drawing, and with this
good composition. Ail this is best learned by
using black lead, black chalk, white chalk, Indian
ink, and these separately or combined, according
VOL. II. D D
402 DRAWING LANDSCAPES.
to the taste of the student ; avoiding colours till
he has made considerable progress.
When colours are employed, they should be
used with great caution and judgment. Nothing
is so disgusting as to see coloured drawings wdiere
the reds, greens, and blues, are laid on in the most
violent manner, without any regard to harmony.
Those who execute such vile daubings will say, in
their defence, that nothing can be greener than
grass, nor bluer than the sky ; but they should
consider, that nature employs such a multitude of
little shadows, and such a variety of different tints
intermixed with her colours, that the harshness of
the original colour is corrected, and the effect of
the whole is very different from a raw and distinct
colour laid upon white paper. Though we should
have recourse to the study of nature, in preference
to any master, for the study of colouring, yet it
requires some judgment to know what part of
nature is to be studied, and what is to be avoided ;
for in nature herself, there are many parts which
are bad ; and to copy them, would do more harm
than good. The student in colouring may exa-
mine, w^ith every possible attention, the colouring
of old walls, broken and stained by time and the
weatlier, old thatch, old tiles, rotten wood ; in
short, all objects which are covered with moss,
stains, and tints of various kinds ; there he v/ill find
all that is most perfect and harmonious in colour-
ing. Let him copy these with every possible care,
and avoid as bad all new buildings, new railing,
and objects which are of a uniform decided colour.
This has been the practice of all the great masters
who have excelled in this captivating part of the
art. In short, after learning the first principles of
DRAWING LANDSCAPES. 40S
drawing, he cannot too soon have recourse to na-
ture ; he will obtain from her the materials for ac-
quiring every species of excellence, in a greater
degree than from the works of- the first masters.
The study of these, however, will greatly abridge
his labour, and it should go hand in hand with
drawing from nature.
The fewer colours that are used in a drawing,
the better, as harmony is most easily preserved;
and by the mixture of a few, every possible tint
may be obtained.
It was mentioned, when treating on optics, that
the sun's rays were considered by Sir Isaac Newton
to be composed of seven primitive colours ; but
all the vast variety of tints which we see in nature
may be formed by the mixture of red, blue, and
yellow, in various proportions. If we had pig-
ments of these colours perfectly pure, w^e should
have no occasion for more than these three ; but
this is not the case, and therefore we are obliged
to have recourse to materials of other broken tints.
The colours that are found to be the most useful in
drawing landscapes in water-colours, are, lakej
indigo, Prussian-hhie, gamboge, light red, yelloxx)
ochre, burnt terra Sienna, hnrnt timber, and Cologne
earth. Some of the other colours may be occasion-
ally useful, but these are all that are necessary for
general use.
The best sort of water-colours are those mixed
with gum and made up into cakes, as these may be
used by rubbing upon a tile, in the same manner as
Indian ink.
Mechanical Drawing.
We have given the name mechanical drawing
to that sort of delineation which depends entirely
D D 2
404 COPYING DRAWINGS.
on geometrical rules, and which is executed by the
use of the ruler and compasses : such as the draw-
ing of plans, elevations and sections of buildings,
machinery, &c. This species of drawing is of very
extensive utility, and is of so easy acquirement
that it may be learned by every person in the same
manner as writing.
For this purpose the geometrical problems should
first be carefully and neatly drawn, and the hand
should be accustomed to the use of the compasses
and drawing-pen. Then the architectural mould-
ings should be studied, as they occur not only in
buildings, but also in cabinet-work, machinery, and
almost all kinds of implements.
In this kind of drawing the outlines of objects
are laid down from actual measurement, by scales
of equal parts; and the lines are drawn first with
black lead pencil, and afterwards with ink, by
means of the steel drawing-pen. The shadows also
are added in Indian ink, and are drawn by rules
that are established with mathematical precision.
OF THE MECHANICAL MEANS FOR COPYING
DRAWINGS.
There are various methods by which those who
are ignorant of the art of drawing may copy very
accurately the outlines of pictures, prints, and
drawings J and these methods are often useful to'
those who can draw, and to engravers, when either
great expedition or great accuracy is required;
though none of them should ever be used by one
who is learning to draw.
Tracing a gainst the Light.
Hold the drawing you wish to copy against one
of the panes of the window j or have a pane of
COPYING DRAWINGS. 405
glass put in a frame, and fitted up like a music-
stand, with a candle behind it. Lay your paper
over your drawing, and you will see all the lines of
the original distinctly through it, by which means
you can easily trace them with a pen or black-lead
pencil.
To make Tracing-Paper.
Mix together equal parts of oil of turpentine and
drying-oil, and with a rag rub it evenly over some
fan, or tissue paper, or any other very thin paper.
Hang it by to dry for a day or two, and it will be
fit for use. Lay this over the print or drawing
you want to copy, and you will see eveiy line dis-
tinctly through, so that you can go over them with
the black-lead pencil. If you wish to do it in ink,
you must mix a little ox's gall with the ink, to
make the paper take it, which it would not other-
wise do on account of the oil.
To make Camp-Paper,
Take some hard soap, mix it with lamp-black;
make it into the consistence of a jelly with water;
with this brush over one side of your paper, and
let it dry. When you use it, put it between two
sheets of clean paper, with its black side down-
wards, and with a pin, or stick with a sharp point,
draw or write what you please upon the clean
paper; and where the tracer has touched, there
will be an impression upon the lowermost sheet of
paper, as if it had been written or drawn with a
pen. It may be made of any colour, by mixing
with the soap black-lead, vermillion, &c.
D D 3
4^ COPYING DRAWINGS.
Stenciling.
Lay the print or drawing you wish to have
copied, over a sheet of paper, and with a pin or
needle prick all the outline over with holes, through
both the papers. Then take the clean paper with
the holes made in it, and lay it upon the paper you
wish to have the design transferred to, and dust it
over with the powder of charcoal in a small muslin
bag J the dust will penetrate through the holes,
and leave a correct copy of the original upon the
paper.
This pricked paper will do again for any number
of copies. This is very useful for ladies who work
flowers upon muslin.
TJie Method of Enlarging and Contracting
by Sqiuires.
Divide the sides of your original with a pair of
compasses into any number of equal parts, and rule
lines across with a black-lead pencil from side to
side, and from top to bottom. Then having your
paper of the size you intend, divide it into the same
number of squares, either laj-ger or less, as you
would enlarge or contract it. Then placing your
original before you, draw, square by square, the
several parts, observing to make the part of the
figure you are drawing fall in the same part of the
squares in the copy, as it does in your original.
To prevent mistakes, number the squares both of
the original and copy. Tins method is much used
by engravers.
To prevent the necessity of ruling across the
original, which in some cases m^ay injure it, take a
square pane of crown glass, and divide its sides, and
PAINTING TRANSPARENCIES. Wf
also its top and bottom into equal parts: then from
each division draw lines across the glass with lamp-
black ground with gum-water, and you will divide
the glass into squares. Then lay the glass upon the
original which you wish to copy, and having drawn
the same number of squares upon your paper, pro-
ceed to copy into each square on your paper what
appears behind each corresponding square of the
glass. Instead of a glass, an open frame with
threads stretched across will answer the same
purpose.
Tlie Pentagraph.
The Pentagraph is an instrument by means of
which one may copy, enlarge, or reduce the out-
lines of any picture, print, or drawing. They may
be had at most mathematical instrument-makers,
and are extremely useful for copying plans, maps,
and other complicated figures.
PAINTING TRANSPARENCIES.
The effect of this kind of painting is very pleas-
ing, if managed with judgment, particularly in fire
and moon lights, where brilliancy of light and
strength of shade are so very desirable.
The very great expence attending the purchase
of stained glass, and the risk of keeping it secure
from accident, almost precludes the use of it in
ornamenting rooms ; but transparencies form a sub-
stitute nearly equal, and at a very small expence.
The paper upon which you intend to paint
must be fixed in a straining-frame, in order that
you may be able to place it between you and the
light, when you see occasion in the progress of
D D 4
408 PAINTING TRANSPARENCIES.
your work. After tracing in your design, the
colours must be laid on in the usual method of
stained drawings. When the tints are got in, you
must place your picture against the window, on a
pane of glass framed for the purpose, and begin
to strengthen the shadows with Indian ink, or with
colours, according as the effect requires, laying the
colours sometimes on both sides of the paper, to
give greater force and depth of colour. The last
touches for giving final strength to shadows and
forms, are to be done with ivory-black, or lamp-
black prepared with gum-water, as there is no
pigment so opaque and capable of giving strength
and decision.
When the picture is finished, and every part has
got its depth of colour and brilliancy, being per-
fectly dry, you touch very carefully with spirits of
turpentine on both sides, those parts which are to
be the brightest, such as the moon and fire, and
those parts requiring less brightness, only on one
side. Then lay on immediately with a pencil, a
varnish made by dissolving one ounce of Canada
balsam in an equal quantity of spirit of turpentine.
You must be cautious with the varnish, as it is apt
to spread. When the varnish is dry, you tint the
flame with red-lead and gamboge, sHghtly tinging
the smoke next the flame: the moon must not be
tinted with colour.
Much depends upon the choice of the subject,
and none is so admirably adapted to this species of
effect as the gloomy Gothic ruin, whose antique
towers and pointed turrets finely contrast their
dark battlements with the pale, yet brilliant moon.
Rays passing througli the ruined windows half
choaked with ivy, a fire amongst the clustering-
pillars and broken monuments of the choir, round
PAINTING TRANSPARENCIES. 409
which are figures of banditti, or others whose hag-
gard faces catch the reflecting hght, afford a pecu-
liarity of effect, not to be equalled in any other
species of painting. Internal views of cathedrals,
also, where windows of stained glass are introduced,
form beautiful subjects.
The great point to be attained is a happy coin-
cidence between the subject and the effect pro-
duced. The fine light should not be too near the
moon, as its glare would tend to injure her pale
silver sight ; those parts which are not interesting
should be kept in an undistinguishable gloom, and
where the principal light is, they should be
marked with precision. Groups of figures should
be well contrasted ; those in shadow crossing those
that are in light, by which means the opposition of
light against shade is effected.
CRAYON-PAINTING
If the limits of our work would have permitted
us, we should have here said something respecting
this branch of the art ; but upon considering that
it is a very inferior mode of painting, being only
adapted for portraits, and being so perishable, that
it is a pity the talents of any eminent artist should
ever be employed in it, we have judged it better to
suppress the article altogether, to make room for
something of more importance. Those who are
desirous of attempting it, may easily be furnished
with the crayons ready prepared; and there is
nothing particular in their use, which may not
be easily acquired by any one who is acquainted
with the practice of drawino-.
410
COLOURS.
We shall now give a brief account of the different
pigments or colours, which are used either in water
or oil, for the purposes of drawing or painting.
Red Colours.
Lakes. This term is used to denote a species of
colours formed by the combination of alumine, or
the oxyd of tin, with the colouring matters of
vegetables.
The lakes chiefly used are red colours, and these
are of different qualities, according to the basis and
colouring matter employed.
The principal lakes are carminey Florence-lake ^
and madder-lake.
Carmine is a very ricli bright crimson colour,
and stands well in water. For the preparation of
carmine, four ounces of finely-pulverized cochineal
are to be poured into four or six quarts of rain, or
distilled water, that has been previously boiled in a
jjervter kettle, and boiled with it for the space of
six minutes longer (some advise to add, during the
boiling, two drachms of pulverized crystals of
tartar). Eight scruples of Roman alum, in pov/der,
are to be then added, and the whole kept upon the
fire one minute longer. As soon as the gross
powder has subsided, and the decoction has become
clear, it is to be carefully decanted into large
cylindrical glasses, covered over, and kept undis-
turbod, till a fine powder is observed to have settled
at the bottom. The liquor is then to be poured
oft from this powder, which is to be gradually dried.
From the liquor, which is still much coloured, the
rest of the colouring matter may be separated by
COLOURS. 411
means of the solution of tin, when it yields a car-
mine little inferior to the former.
Floroitine lake is the kind in general use, known
by the name of lake. It is used in water and also
in oil, but does not stand, which is much to be
lamented, as it is a very beautiful colour, and the
is no substitute that Vv^ill completely answer all the
purposes of lake.
The best sort may be prepared from the sedi-
ment of cochineal that remains in the kettle after
making carmine, adding to it a small quantity of
cochineal, or Brazil-wood, and precipitating the
colouring matter with a solution of tin.
Madder-lake is not so bright and rich a colour
as the last-mentioned lakes, but has this valuable
advantage, that it stands much better, and it may
answer many of the purposes of Florence-lake.
It is prepared nearly in the same manner as the
foregoing.
Rose-lake., This is generally called rose-pink.
It is a lake made by a basis of chalk, coloured by
Brazil or Campeachy v.^ood. It does not stand,
and is only used for house-painting and paper-
hanging.
VermilUon, a bright scarlet pigment, formed
from sulphur and quicksilver. Its goodness is
known by its brightness, and by its inclining to a
crimson hue. It is a very useful colour in oil,
where it stands very well 5 but in water it is apt to
turn black.
Red lead, or minium^ is lead calcined till it ac-
quires a red colour, by exposing it V\dth a large
surface to the fire. This colou.r is very apt to turn
black in water, and is therefore seldom used.
Indian red. This colour is sometimes employed
to answer some of the pui'poses of lake. It is
412 COLOURS,
difficult to procure the genuine kind, which comes
from the East Indies. What is sold for Indian
red, is said to be chiefly made in this country.
Venetian red is a nativ e red ochre, rather inclin-
ing to the scarlet than the crimson hue : it is not
far different in colour from the common Indian
red, and is a very good colour.
Spanish'hrown is also an earthy substance, found
in the same state in which it is used ; it is nearly
of the same colour as Venetian red, but coarser.
It is only used for the commonest purposes.
Light red, or burnt ochre. This is common
yellow ochre heated red-hot in the fire, till the
colour changes from yellow to a red. It is a very
excellent colour, both in water and oil, having the
quality in common with all the ochres, of standing
perfectly well.
Red chalk. This is the same substance as is
used for drawing on paper, in the manner of a
crayon. It is very much like light red, and is used
instead of it, for some purposes. It stands per-
fectly well, and may be used both in water and oil.
Burnt Terra Sienna. This colour is made by
calcining raw terra Sienna till it acquires a red
colour. It is of a very rich tint, and is much used
both in water and oil. It stands well in both.
Blue Colours.
Ultramarine is prepared from lapis lazxdi, by
calcining and washing it very clean. When ge-
nuine, it is an extremely bright blue colour, some-
what transparent both in oil and water, and stands
perfectly. On these accounts it is of the utmost
value, being excellent in every kind of painting,
COLOURS. 413
even in enamel ; but the great price prevents the
general use of it.
Ultramarine ashes. This is the residuum after
washing the lapis lazuli, in which a portion of the
ultramarine still remains. It is very subject to be
adulterated. It is not so bright as ultramarine,
being, like that colour, with a tint of red and white
in it. When genuine it stands well.
, i Prussian blue. This colour is iron combined
with the prussic acid. It is made in the following
manner.
Two parts of purified potash are most intimately
blended with three parts of dried and finely pul-
verized bullock's blood. The mass is first calcined
in a covered crucible, and on a moderate fire, until
no more smoke or flame appear ; and it is after
this brought to a complete, yet moderate, ignition.
Or equal parts of potash and finely-powdered coals,
prepared from bones, horns, claws, &c. are min-
gled, and heated in a covered crucible to a moderate
redness. This done, either of these two calcined
masses is, after cooling, lixiviated with boiling
water, and the lixivium filtered. Nothing remains
now but to make a solution of one part of green
vitriol and two parts of alum, and to add to it
while yet hot the above lixivium, little by little how-
ever, and to separate the greenish-blue precipitate,
which then forms by means of a filtre. If after-
wards a slight quantity of diluted muriatic acid be
affused upon this precipitate, it assumes a beautiful
dark-blue colour. The operation is terminated
by edulcorating and drying the pigment thus
prepared. Prussian-blue is an extremely beau-
tiful colour when properly prepared, and stands
well. Common Prussian-blue is apt to contain
some iron, which causes it to turn greenish or olive.
414 coLOimSi
Verditer is a blue pigment, obtained by adding
chalk or whitening to the solution of copper in
aqua fortis. The best sort is prepared by the
refiners, who employ for this purpose the solution
of copper, which they obtain in the process of
parting, by precipitating silver from aqua fortis by
plates of copper. Common verditer is made from
the sulphate of copper, or blue, by the manufac-
turers in Sheffield and Birmingham. Verditer is
only used for very coarse purposes, chiefly by the
paper-stainers. It has been sometimes called
Sanders blue, from ignorance of the meaning of
the term cendres blues, or blue ashes, which the
l^rench call it.
Indigo. This colour is extracted from a plant
called Anil, that grows in the East and West
Indies. It is not so bright as Prussian-blue, but it
is cooler, and has the advantage of being very
durable. When dissolved by the sulphuric acid,
it forms Scott's liquid blue, so much used for
colouring silk stockings, &c.
Smalt. This is glass coloured with cobalt, and
oi'ound to a line powder. Its coarseness prevents
its being used much for painting in oil or water.
It is employed sometimes by stervving it upon a
ground of oil-paint. It is also used in enamel-
painting. It stands well.
Blue Bice. This is only smalt more finely levi-
gated.
Yellow Colours.
Indian yellow. This is the brightest of all yel-
lows for water-colours, and is perfectly durable.
It is said to be procured from the urine of the
COLOURS. 415
bufFalo. In the East Indies it is a very common
and cheap colour ; the natives there use it com-
monly for colouring their calicoes, which they do
without any mordant, so that the colour is washed
out again when the cloth is dirt}'.
King's 1/elloxv. This colour is orpiment refined,
which is a substance dug out of the earth, and
consists of sulphur joined to arsenic ; or it may be
prepared by subliming sulphur with arsenic. It is
of a very bright yellow, but does not stand very
well ; and great caution should be used in employ-
ing it, as it is a strong poison.
Naples yelloxc. This is a very durable and bright
pale yellow ; it comes from Naples, and is supposed
to be prepared from lead and antimony.
Yellow ochre. This is an earth coloured by
oxyd of iron. It is a cheap colour, and not very
bright ; but is valuable on account of its standing
well.
Roman ochre. This is a superior kind of yellow
ochre.
Dutch pink. This pigment is formed of chalk
coloured with the juice of French berries, or
other vegetables affording a yellow colour. It
does not stand, and is chiefly used for common
purposes.
Gamboge is a gum brought from the East Indies.
It readily dissolves in water, and is a fine bright
yellow. It is used only in water, and is very
serviceable.
Massicot is an oxyd of lead, prepared by calcin-
ing white-lead. It is very little used, the colour
not being very bright.
Gall stones. This is a concretion or hard sub-
stance, formed in the gall-bladders of beasts j or it'
416 COLOURS.
may be obtained from the gall of animals. It is
a very rich colour, but does not stand.
Raw Terra Sienna^ is a native ochrous earth
brought from Italy. It is a fine warm colour, and
stands well.
French berries. A liquor may be extracted
from these, which is useful as a stain for some
coarse purposes ; but it does not keep its colour.
Turmeric root, and sqffro?i, may be used for si-
milar purposes.
Ora7ige lake is the tinging part of annatto pre-
cipated together with the earth of alum. It does
not stand.
Brown pinli is the tinging part of some vegeta-
ble substance precipitated upon the earth of alum.
It is of a fine rich greenish yellow, but does not
stand in water.
Green Colours.
There are few colours that are useful as greens ;
accordingly, it is the practice with artists, to form
their greens by the mixture of blue and yellow
colours. By varying these, a vast variety of" green
tints may be obtained.
Sap green. This colour is the concreted juice
of the buckthorn-berries. It is never used in oil.
It is employed chiefly in flower-painting and co-
louring prints, he.
Ve?Yl?gris. If plates of copper, moistened from
time to time with vinegar, be left exposed to the
air, they will be converted into a green oxyd,
Called verdigris : this is an imperfect oxyd of
copper, combined with a small portion of acetic
acid, carbonic acid, and water. It is prepared in
COLOURS. 4^17
large quantities, chiefly in France near Montpel-
lier, by stratifying copper-plates with the husks of
grapes yet under vinous fermentation, which soon
grow acid, and corrode the copper. After the
plates have stood in this situation for a sufficient
time, they are moistened with water, and exposed
in heaps to the air. The verdigris is scraped off
from their surface as it forms.
Verdigris is of a bluish-green colour, but has no
body, and does not stand. It is only used for
very coarse purposes. It answers best when used
in varnishes.
Distilled verdigris^ sometimes called crystals of
verdigris, is prepared from common verdigris, by
dissolving it in vinegar. It is of a very bright
green, and is used chiefly for varnishes, and in co-
louring maps, &c.
Brown Colours.
Bistre is the finer part extracted from the soot
of burnt wood. It is much used for sketches in
water-colours, being a transparent warm colour.
Cologne earth. This is a mineral substance of
a dark blackish brown colour. It is a very useful
colour ; though what is generally sold in the shops
for Cologne earth is an artificial mixture of several
colours.
Raw timbre is a native ochreous earth, of a light
brown. It stands well.
Burnt umhre. This is only the last mentioned ,
colour, calcined in the fire. It then acquires a rich
deep brown, and is of great use, being a fine
colour, and standing perfectly well.
Asphaltum. This colour is used in oil, and is of
a very rich deep brown. It is a transparent or
glazing colour. It will not work in water, but
VOL. II. E E
4-18 COLOURS.
when dissolved in turpentine, it becomes a useful
substance for giving deep and spirited touches to
drawings.
White Colours.
Flake White is corbonate of lead, formed by cor-
roding lead with vegetable acids, or vinegar.
White-lead is the same colour as flake white, only
of an inferior quality. It is the only white used
in oil-painting, and is a very useful colour •, but in
water it always turns black, and should never be
used.
Pure carbonate of lime is very useful as a white
in water-colours, as it stands perfectly well.
Egg-sJiell white, and oyster-shell tchite, are only
egg-shells, or oyster^shelis calcined, by which the
animal gluten is destroyed, leaving the lime be-
hind, which soon attracts the carbonic acid again
from the atmosphere. Well washed Spanish white,
or common whitening, answers tlie same purpose.
Black Colours.
Lamp black is the soot of oil, collected after it
is formed by burning. It is very generally used,
both in oil and water, and stands perfectly well.
Ivory black is the coal of ivory or bone, formed
by giving them a great heat, while they are de-
prived of all access of air. It is of a more intense
black than lamp black.
Blue black is the coal from burning vine-stalks
in a close vessel. It is like ivory black, with a tint
of blue.
Indiaii ink has been already described in page
S46.
419
OF ENGRAVING.
Engravings or graving, as it is sometimes called,
is the cutting lines upon a copper-plate, by meaps
of a steel instrument, called a graver.
This was the first way of producing copper-pl^te
prints that was practised, and is still much i^sed in
historical subjects, portraits, and in finishing land-
scapes.
The tools necessary for this art are, gravers, a
scraper, a burnisher, an oil-stone, a sand-bag, an
oil-rubber, and some good charcoal.
The gravers are instruments of tempered steel,
fitted into a short wooden handle. They are of
two sorts, square and. lozenge : the first is used iji
cutting very broad strokes, the other for fainter
and more delicate lines.
The scraper is a three-edged tool, for scrapii^g
off the burr raised by the graver. Burnishers ar.e
for rubbing down any lines that are too deep, or
burnishing out any scratches or holes i^ the cop-
per: they are of very hard steel, wejl rounded
and polished.
The oil-stone is for whetting the gravers, etch-
ing-points, &c.
The sand-bag, or cushion, is for laying the plate
upon, for the conveniency of turning ijt r,ound in
any direction.
The oil-rubber and charcoal are for polishing
the plate when necessary.
As great care is required to whet the graver
nicely, particularly tlie beljy of it, the two an^le^s
of the graver which are to be held next the pliajte,
must be laid flat upon the stone, and rubbed
steadily, till the belly rises gradually above the
E E 2
420 ENGRAVING.
plate, so as that, when you lay the graver flat
upon it, you may just perceive the light under
the point ; otherwise it will dig into the copper,
and then it will be impossible to keep a point, or
execute the work with freedom. In order to this,
keep your right arm close to your side, and place
the fore-finger of your left hand upon that part of
the graver which lies uppermost on the stone.
When this is done, in order to whet the face, place
the flat part of the handle in the hollow of your
hand, with the belly of the graver upwards, upon
a moderate slope, and rub the extremity, or face,
upon the stone, till it has an exceedingly sharp
point, w^hich you may try upon your thumb-nail.
When the graver is too hard, as is usually the
case when first bought, and which may be known by
the frequent breaking of the point, the method of
tempering it is as follows : Heat a poker red-hot, and
hold the graver upon it, within half an inch of the
point, till the steel changes to a light straw colour ;
then put the point into oil, to cool ; or hold the
graver close to the flame of a candle, till it be of
the same colour, and cool it in the tallow ; but be
careful either way, not to hold it too long, for then
it will be too soft ; and in this case the point,
which will then turn blue, must be tempered
again. Be not too hasty in tempering ; for some-
times whetting will bring it to a good condition,
w^hen it is but a little too hard.
To hold the graver, cut off that part of the
handle which is upon the same line with the belly,
or sharp edge of the graver, making that side flat,
that it may be no obstruction.
Hold the handle in the hollow of your hand;
and, extending your fore-finger towards the point,
let it rest on the back of the graver, that you may
ENGRAVING. 421
guide it flat and parallel with the plate. Take
care that your fingers do not interpose between
the plate and the graver ; for they will hinder you
from carrying the graver level with the plate, and
from cutting your strokes so clean as they ought
to be.
To lay the design upon the plate, after you
have polished it fine and smooth, heat it so that
it will melt virgin-wax, with which rub it thinly
and equally over, and let it cool. Then the de-
sign which you lay on must be drawn on paper,
with a black-lead pencil, and laid upon the plate,
with its pencilled side upon the wax ; press it
down, and with a burnisher go over every part of
the design, and when you take off the paper, you
will find every line upon the waxed plate which
you drew with the black lead pencil ; then with a
sharp pointed tool trace all your design through
the wax upon the plate, and you may then take
off the wax, and proceed to work.
Let the table, or board you work at, be firm
and steady ; upon which place your sand-bag with
the plate upon it ; and, holding the graver as above
directed, proceed in the following manner.
For straight strokes, hold your plate firm upon
the sand-bag with your left hand, moving your
right hand forwards; leaning lighter where the
stroke should be fine, and harder where you would
have it broader.
For circular or crooked strokes, hold the graver
stedfast, moving your hand or the plate, as you
see convenient.
Learn to carry your hand with such dexterity,
that you may end your stroke as finely as you
began it ; and if you have occasion to make one
part deeper or blacker than another, do it by de-
E E 3
422 ENGRAVING*
grees ; and that you may do it ^vith greater exact-
ness, take care that your strokes be not too close
nor too wide.
In the course of your v/ork scrape off the
roughness which arises, with your scraper; but
be careful, in doing this, not to scratch the plate ;
and that you may see your work properly as you
go on, rub it with the oil-rubber, and wipe the
plate clean, which will take off the glare of the
copper, and show what you have done to the best
advantage.
Any mistakes or scratches in the plate may be
rubbed out with the burnisher, and tlie part levelled
with the scraper, polishing it again afterwards
lightly with the burnisher, or charcoal.
Having thus attained the use of the graver, ac-
cording to the foregoing rules, you will be able to
finish the piece you had etched, by graving up the
several parts to the colour required ; beginning, as
in the etching, with the fainter parts, and advanc-
ing gradually with the stronger, till the v/hole is
completed.
The dry point or needle (so called because not
used till the ground is taken off the plate) is prin-
cipally employed in the extremely light parts of
water, sky, drapery, architecture, &c.
To prevent any obstruction from too great a
degree of light, the use of a sashj made of trans-
parent, or fan paper, pasted on a fiamc, and placed
sloping at a convenient distance between your
work and the lights will preserve the sight ; and
when the sun shines, it cannot possibly be dis-
pensed with.
4>23
ETCHING.
Etching is a manner of engraving on copper,
in which the lines or strokes, intead of being cut
with a tool or graver, are corroded in with aqua
fortis.
It is a much later invention than the art of en-
graving by cutting the lines on the copper, and
has many advantages over it for some purposes,
though it cannot supersede the use of the graver
entirely, as there are many things that cannot be
etched so well as they can be graved.
In almost all the engravings on copper that are
executed in the stroke manner, etching and graving
are combined, the plate being generally begun by
etching, and finished with the graver. Landscapes,
architecture, and machinery, are the subjects that
receive most assistance from the art of etchinsr ;
for it is not so applicable to portraits and historical
designs.
We shall first describe the various instruments
and materials used in the art.
Copper-plates may be had ready prepared at the
coppersmiths, by those who reside in large towns ;
but when this cannot be had, procure a piece of
pretty thick sheet-copper from a brazier, rather
larger than your drawing, and let him planish it
well ; then take a piece of pumice-stone, and with
water rub it all one way, till the surface is as
smooth and level as it can be made by that means :
a piece of charcoal is next used with water, for
polishing it still farther, and removing the deep
E E 4
4f24 ETCHING.
scratches made by the pumice-stone ; and it is then
finished with a piece of charcoal of a finer grain,
with a Uttle oil.
Etching-points or 7ieedles are pointed instruments
of steel, about an inch long, fixed in handles of
hard wood, about six inches in length, and of the
size of a goose-quill. They should be well tem-
pered, and very accurately fixed in the centre of
the handle. They must be brought to an accu-
rately conical point, by rubbing upon an oil-stone,
with which it is also very necessary to be provided.
Several of these points will be necessary.
A parallel-ruler is necessary for drawing parallel
straight lines with. This is best when faced with
brass, as it is not then so liable to be bruised by
accident.
Compasses aj'e useful for striking circles and
measuring distances.
Aqua fortis, or what is better, spirits of nitre,
(nitrous acid,) is used for corroding the copper, or
hiting-in, as it is called. This must be kept in a
bottle with a glass stopple, for its fumes destroy
corks. A stopple made of wax will serve as a sub-
stitute, or a cork well covered with wax.
Bordering-xvaa\ for surrounding the margin of
the copper-plate when the aqua fortis is pouring
on. This may be bought ready prepared, but it
may be made as follows.
Take one-third of bees-wax to two-thirds of
pitch J melt them in an iron ladle, and pour them,
when melted, into v/ater lukewarm ; then mould it
with your hand till it is thoroughly incorporated,
and all the water squeezed out. Form it into rolls
of convenient size.
Turpentine varnish, is used for covering the cop-
per-plate with, in any part where you do not wish
ETCHING. ' 425
the aqua fortis to bite. This may be diluted to a
proper consistence with turpentine, and mixed
with lamp-black, that it may be seen better when
laid upon the pkite.
Ectching-ground is used for covering the plate
all over with, previous to drawing the lines on it
with the needles. It is prepared in the following
manner.
Take of virgin-wax and asphaltum, each two
ounces, of black pitch and Burgundy pitch, each
half an ounce ; melt the wax and pitch in a new
earthenware glazed pipkin, and add to them, by
degrees, the asphaltum, finely powdered. Let the
whole boil till such time as that, by taking a drop
upon a plate, it will break when it is cold, on bend-
ing it double two or three times between the fingers.
The varnish, being then enough boiled, must be
taken off from the fire, and letting it cool a little,
must be poured into warm water, that it may work
the more easily with the hands, so as to form into
balls for use.
It must be observed, first, that the fire be not
too violent, for fear of burning the ingredients ;
a slight simmering will be sufficient j secondly,
that while the asphaltum is putting in, and even
after it is mixed with them, the ingredients should
be stirred continually with a spatula ; and thirdly,
that the water into which this composition is
thrown, should be nearly of the same degree of
warmth with it, to prevent a kind of cracking,
which happens when the water is too cold.
The varnish ought always to be harder in sum-
mer than winter, and it will become so if it be
suffered to boil longer, or if a greater proportion of
the asphaltum be used. The experiment above
mentioned, of the drop suffered to cool, will de-
4S6 ETCHING.
termine the degree of hardness or softness that
may be suitable to the season when it is used.
To lay the ground for etching, proceed in the
following manner : Having cleaned the copper-
plate with some fine whiting and a linen rag, to
free it from all grease, fix a hand-vice to some part
of it where no work is intended to be, to serve as a
handle for managing it by when warm. Roll up
some coarse brown paper, and light one end ; then
hold the back of the plate over the burning paper,
moving it about until every part of it. is equally
heated, so as to melt the etching-ground, which
should be wrapped up in a bit of taflfety, to prevent
any dirt that may happen to be among it, from
mixing with what is melted upon the plate. If
the plate be large, it will be best to heat it over a
chafing-dish with some clear coals. It must be
heated just sufficient to melt the ground, but not
so much as to burn it. When a sufficient quantity
of the etching-ground has been rubbed upon the
plate, it must be dabbed, or beat gently, while the
plate is hot, with a small dabber, made of cotton,
wrapped up in a piece of tafFety, by which oper-
ation the ground is distributed more equally over
the plate than it could be by any other means.
When the plate is thus uniformly and thinly
covered with the varnish, it must be blackened by
smoking it with a wax taper. For this purpose
twist together three or four pieces of wax taper, to
make a larger flame, and while the plate is still
warm, hold it with the varnished side downwards,
and move the smoky part of the lighted taper over
its surface, till it is made almost quite black ; taking
care not to let the wick touch the varnish, and that
the latter get no smear or stain. In laying the etch-
ing-ground, great care must be taken that no par-
ETCHING}. 427
tides of dust or dirt of any kind settle upon it, as
that would be found very troublesome in etching ;
the room, therefore, in which it is laid should be
as still as possible, and free from dust*
The ground being now laid) and suffered to
cool, the next operation is to transfer the design to
the plate.
For this purpose a tracing on oiled paper must
now be made, from the design to be etched, with
pen and ink, having a very small quantity of ox's
gall mixed with it, to make the oiled paper take it;
also a piece of thin paper, of the same size, must
be rubbed over with red chalk, powdered, by
means of som.e cotton i Tlien laying the red
chalked paper, with its chalked side next the
ground, on the plate, put the tracing over it, and
fasten them both together, and to the plate, by a
little bit of the bordering wax.
When all this is prepared, take a blunt etching
needle, and go gently all over the lines in the
tracing ; by which means the chalked paper will
be pressed against the ground, and the lines of
the tracing will be transferred to it : on taking
off the papers, they will be seen distinctly.
The plate is now prepared for drawing through
the lines which have been marked upon the
ground. For this, the etching-points or needles
are employed, leaning hard or lightly, according
to the degree of strength required in the lines.
Points of different sizes and forms are also usedj
for making lines of different thickness, though
commonly this is effected by the biting-in with the
aqua fbrtis.
A margin or border of wax must now be formed
all round the plate, to hold the aqua fortis when it
is poured on. To do this, the bordering wax
428 ETCHING.
already described must be put into lukewarm
water to soften it, and render it easily worked by
the hand. When sufficiently pliable, it must be
drawn out into long rolls, and put round the edges
of the plate, pressing it down firm, and forming it
with the fingers into a neat wall or margin. A spout
must be formed in one corner, to pour off the aqua
fortis by afterwards.
The nitrous acid (spirits of nitre) is now to be
diluted with four or five times as much water, or
more (according as you wish the plate to be bit
quick or slow,) and poured upon the plate. In a
few minutes you will see minute bubbles of air
filling all the lines that have been drawn on the
copper, which are to be removed by a feather ; and
the plate must be now and then swept, as it is
called, or kept free from air bubbles. By the more
or less rapid production of these bubbles, you
judge of the rapidity with which the acid acts upon
the copper. The biting-in of the plate is the most
uncertain part of the process, and nothing but very
great experience can enable any one to tell w^hen
the plate is bit enough, as you cannot easily see
the thickness and depth of the line till the ground
is taken off.
When you judge, from the time the acid has
been on, and the rapidity of the biting, that those
lines which you wish to be the faintest are as deep
as you wish, you pour off the aqua fortis by the
spout, wash the plate with water, and dry it, by
blowing with bellows, or by the iire, taking care
not to melt the ground.
Those lines that are not intended to be bit any
deeper, must now be stopped up with turpentine-
varnish mixed with a little lamp-black, and laid on
with a camel's-hair pencil ; and when this is
ETCHING. 429
thoroughly dry, the aqua tbrtis may be poured on
agahi, to bite the other hues that are required to
be deeper.
This process of stopping-out and biting-in is to
be repeated as often as there are to be lines of dif-
ferent degrees of thickness, taking care not to
make any mistake in stopping-out wrong lines.
It is also necessary to be particularly careful to
stop-out with the varnish, those parts from which
the ground may happen to have come off by the
action of the acid, otherwise you will have parts
bit that were not intended, which is csdledjoul-
biting.
When the biting-in is quite finished, the next
operation is to remove the bordering-wax and the
ground, in order that you may see what success
you have had ; for till then, this cannot be known
exactly.
To take off the bordering-wax, the plate must
be heated by a piece of lighted paper, which soft-
ens the wax in contact with the plate, and occa-
sions it to come off quite clean.
Oil of turnpentine is nov/ poured upon the
ground, and the plate is rubbed with a bit of linen
rag, which removes all the ground. Lastly, it is
cleaned off with whitening.
The success of the etching may now be known,
but it is necessary to get an impression taken upon
paper by a copper-plate printer. This impression
is called a proof.
If any parts are not bit so deep as were in-
tended, the process may be repeated, provided the
lines are not too faintly bit to admit of it. This
second biting-in the same lines, is called re-bitingy
and is done as follows : Melt a little of the etching-
ground on a spare piece of copper, and dab it a
430 ETCHING.
little, to get some on the dabber; then, having
cleaned out, with whiting, the lines that are to be
re-bit, heat the plate gently, and dab it very lightly
with the dabber. By this, the parts between the
lines will be covered v/ith the ground, but the lines
themselves will not be tilled up, and consequently
will be exposed to the action of the aqua fortis.
This is a very delicate process, and must be per-
formed with great care. The rest of the plate
must now be varnished over, the bordering wax
put on again, and the biting repeated in the same
manner as at first.
If any part should be bit too deep, it is more
difficult to recover it, or make it fainter : this is ge-
nerally done by burnishing the part down, or rub-
bing it with a piece of charcoal. This will make
the lines shallower, and cause them not to print so
black.
Should any small parts of the lines have missed
altogether in the biting, they may be cut with the
graver ; which is also sometimes employed to cross
the lines of the etching, and thus to work up a
more finished effect.
Dry-pointing is another method employed for
softening the liarsh effects usually apparent in an
etching. This is done by cutting with the etching-
point upon the copper without any ground or var-
nish, which does not make a very deep line, and is
used for covering the light, where very delicate
tints and soft shadows are wanting. By varying
these processes of etching, graving, and dry-point-
ing, as is thought necessary, the plate is worked
up to the full effect intended j and it is then sent
to the writing engraver, to grave whatever letters
may be required to be put upon it.
431
MEZZOTINTO SCRAPING.
This art is of later origin than the last, and is not
of such difficult execution. In mezzotinto prints
the shadows are not formed by lines or hatches, but
much resemble Indian ink. It differs in the pro-
cess, however, from aquatinta, although the effect is
not very different.
Mezzotinto is chiefly employed in portraits and
historical subjects ; and aqua tinta for landscape
and architecture.
The tools necessary for mezzotinto scraping are
the grounding-tool, burnishers, and scrapers.
To lay the mezzotinto ground, lay your plate,
with a piece of flannel under it, upon your table;
hold the grounding-tool in your hand perpendi-
cularly ; lean upon it moderately hard, continually
rocking your hand in a right line from end to end,
till you have wholly covered the plate in one di-
rection : next cross the strokes from side to side,
afterwards from corner to corner, working the tool
each time all over the plate, in every direction,
almost like the points of a compass ; taking all
possible care not to let the tool cut (in one direc-
tion) twice in a place. This done, the plate will
be full, or, in other words, all over rough alike, and
would, if it were printed, appear completely black.
Having laid the ground, take the scrapings of
black chalk, and with a piece of rag rub it over the
plate ; or you may smoke it with candles, as before
directed, for etching.
Now take your drawing, and having rubbed the
black with red chalk-dust, mixed with flake-white,
proceed to trace it on the plate.
4^2 AQUA TINTA.
To form the lights and shadows, take a blunt
needle, and mark out the outlines only, then with
a scraper scrape off the lights in every part of the
plate, as clean and smooth as possible, in propor-
tion to the strength of the lights in your drawing,
taking care not to hurt your outlines.
The use of the burnisher is to soften or rub
down the extreme light parts after tlie scraper is
done with ; such as the tip of the nose, forehead,
linen, &c. which might otherwise, when proved,
appear rather misty than clear.
Another method used by mezzotinto scrapers,
is, to etch the outlines of the original, as also the
folds in drapery, making the breadth of the sha-
dows by dots, which having bit to a proper depth
with aqua fortis, they take oft' the ground used in
etching, and having laid the mezzotinto ground,
proceed to scrape as above.
When your plate is ready for taking a proof or
impression, send it to the copper-plate printer, and
get it proved. When the proof is dry, touch it
with white chalk where it should be lighter, and
with black chalk where it should be darker ; and
when the print is retouched, proceed as before, for
the lights ; and for the shades use a small ground-
ing-tool, as much as you judge necessary to bring
it to a proper colour ; and when you have done as
much as you think expedient, prove it again ; and
so proceed to prove and touch till it is entirely to
your mind.
AQUA TINTA.
Aqua'tinia is a method of producing prints very
much resembling drawings in Indian-ink.
ENGRAVING IN AQUA TINTA. 433
The principle of the process consists in corrod-
ing tlie copper with aqua fortis, in such a manner,
that an impression from it has the appearance of a
tint laid on the paper. This is effected by cover-
ing the copper with a powder, or some substance
which takes a granulated form, so as to prevent the
aqua fortis from acting where the particles adhere,
by this means causing it to corrode the copper
partially, and in the interstices only. When these
particles are extremely minute and near to each
other, the impression from the plate appears to the
naked eye exactly like a wash of Indian-ink ; but
when they are larger, the granulation is more dis-
tinct ; and as this may be varied at pleasure, it is
capable of being adapted with great success, to a
variety of purposes and subjects.
This powder, or granulation, is called the aqua^
tinta grai?iy and there are two general modes of
producing it.
We shall first describe what is called the powder-
grain, because it was the first that was used.
Having etched the outline on a copper-plate,
prepared in the usual way by the coppersmith (for
which see tlie article etching), some substance
must be finely powdered and sifted, which will melt
with heat, and when cold will adhere to the plate,
and resist the action of aqua fortis. The sub-
stances which have been used for tliis purpose,
either separately or mixed, are asphaltum, Bur-
gimdy-pitch, rosin, gum-copal, gum-mastich ; and in
a greater or less degree, all the resins and gum-
resins will answer the purpose. Common rosin
has been most generally used, and answers toler-
ably well ; tliough gum-copal makes a grain that
resists the aqua fortis better.
VOL. ir, F F
434 ENGRAVING IN AQUA TINTA.
The substance intended to be used for the grain
must now be distributed over the plate as equally
as possible ; and different methods of performing
this essential part of the operation have been used
by different engravers, and at different times.
The most usual way is to tie up some of the
powder in a piece of muslin, and strike it against a
piece of stick held at a considerable height above
the plate; by this, the powder that issues falls
gently, and settles equally over the plate. Every
one must have observed how uniformly hair-powder
settles upon the furniture after the operations of
the hair-dresser. This may afford a hint towards
the best mode of performing this part of the pro-
cess. The powder must fall upon it from a con-
siderable height, and there must be a sufficiently
large cloud of the dust formed. The plate being
covered equally over with the dust, or powder, the
operator is next to proceed to fix it upon the plate,
by heating it gently, so as to melt the particles.
This may be effected by holding under the plate
lighted pieces of brown paper, rolled up, and
moving them about till every part of the powder is
melted ; this will be known by its change of colour,
which will turn brownish. It must now be suffered
to cool, when it may be examined with a magnifier,
and if the grains or particles appear to be uni-
formly distributed, it is ready for the next part of
the process.
The design or drawing to be engraved must now
be examined, and sucli parts of it as are perfectly
wnite are to be remarked. Those corresponding
parts of the plate must be covered, or stopped out
(as it is called) with turpentine-varnish, diluted with
turpentine to a proper consistence to work freely
ENGRAVING IN AQUA TINTA. 43^
with the pencil, and mixed with lamp-black to give
it colour ; for if transparent, the touches of the
pencil would not be so distinctly seen. The mar-
gin of the plate must also be covered with varnish.
When the stopping out is sufficiently dry, a border
of wax must be raised round the plate, in the same
manner as in etching, and the aqua fortis properly
diluted with water poured on. This is called biting
in, and is the part of the process which is most
uncertain, and which requires the greatest degree
of experience. When the aqua fortis has lain on
so long that the plate, when printed would produce
the lightest tint in the drawing, it is poured off,
and the plate washed with water, and dried. When
it is quite dry, the lightest tints in the drawing are
stopped out, and the aqua fortis poured on as be-
fore, and the same process is repeated as often as
there are tints to be produced in the plate.
Although many plates are etched entirely by this
method of stopping out and biting in alternately,
yet it may easily be conceived, that in general, it
would be very difficult to stop round, and leave out
all the finishing touches, as also the leaves of trees
and many other objects, which it would be impos-
sible to execute with the necessary degree of free-
dom, in this manner.
To overcome this difficulty, another very ingeni-
ous process has been invented, by which these
touches are laid on the plate with the same ease and
expedition as they are in a drawing in Indian-ink.
Fine \vashed whiting is mixed with a little treacle
or sugar, and diluted with water in the pencil, so
as to work freely, and this is laid on the plate
covered with the aqua-tint ground, in the same
manner, and on the same parts as ink on the draw-
ing. When this is dry, the whole plate is varnished
FF 2
436 ENGRAVING IN AQUA TINTA.
over with a weak and thin varnish of turpentine,
asphaltum, or mastich, and then suffered to dry,
when the aqua fortis is poured on. The varnish
will immediately break up in the parts where the
treacle mixture was laid, and expose all those places
to the action of the acid, while the rest of the plate
remains secure. The effect of this will be, that all
the touches or places where the treacle was used
will be bit in deeper than the rest, and will have all
the precision and firmness of touches in Indian-ink.
After the plate is completely bit in, the border-
ing-wax is taken off, by heating the plate a little
with a lighted piece of paper ; and it is then cleared
from the ground and varnish by oil of turpentine,
and wiped clean with a rag and a little fine w^hiting,
when it is ready for the printer.
The principal disadvantages of this method of
aqua-tinting are, that it is extremely difficult to
produce the required degree of coarseness or fine-
ness in the grain, and that plates so engraved do
not print many impressions before they are worn
out. It is therefore now very seldom used, though
it is occasionally of service.
We next proceed to describe the second method of
producing the aqua-tint ground, which is generally
practised. Some resinous substance is dissolved
in spirits of wine, as common resin, Burgundy-
pitch, or mastich, and this solution is poured all
over the plate, wdiich is then held in a slanting
direction, till the superfluous fluid drains ofl'j and
it is then laid down to dry, which it does in a few
minutes. If the plate be then examined with the
magnifier, it \\i\\ be found that the spirit, in evapor-
ating, has left the resin in a granulated state, or
rather, that the latter has cracked in every direc-
tion, still adhering firmly to the copper.
ENGRAVING IN AQUA TINTA. 437
A grain is tlms produced with the greatest ease,
which is extremely regular and beautiful, and
much superior for most purposes to that produced
by the former method. After the grain is formed,
every part of the process is conducted in the same
manner as above described.
Having thus given a general idea of the art, we
shall mention some particulars necessary to be
attended to, in order to ensure success in the oper-
ation. The spirits of wine used for the solution,
must be highly rectified, and of the best quality.
What is sold in the shops generally contains cam-
])hor, which would entirely spoil the grain. Resin,
Burgundy-pitch, and gum mastich, when dissolved
in spirits of wine, produce grains of a different
appearance and figure, and are sometimes used
separately, and sometimes mixed in different pro-
portions, according to the taste of the artist, some
using one substance, and some another. In order
to produce a coarser or finer grain, it necessary to
use a greater or smaller quantity of resin; and to
ascertain the proper proportions, several spare pieces
of copper must be provided, on which the liquid
may be poured, and the grain examined, before it is
applied to the plate to be engraved. After the
solution is made, it must stand still and undisturbed
for a day or two, till all the impurities of the resin
have settled to the bottom, and the fluid is quite
pellucid. No other method of freeing it from those
impurities has been found to answer ; straining it
through linen or muslin, only fills it with hairs,
which are ruinous to the grain. The room in which
the liquid is poured on the plate must be perfectly
still and free from dust, which, whenever it falls on
the plate while wet, causes a white spot, which it is
impossible to remove without laying the grain
FF 3
438 ENGRAVING IN AQUA TINTA.
a-fresh. The plate must also be previously cleaned,
with the greatest possible care, with a rag and
whiting, as the smallest stain or particle of grease
produces a streak or blemish in the grain. All
these attentions are absolutely necessary to produce
a tolerably regular grain ; and, after every thing
that can be done by the most exprienced artists,
still there is much uncertainty in the process. They
are sometimes obliged to lay on the grains several
times, before they procure one sufficiently regular.
The same proportions of materials do not always
produce the same effect, as it depends in some
degree on their qualities: and it is even materially
altered by the weather. These difficulties are not
to be surmounted but by a great deal of experience j
aad those who are daily in the habit of practising
the art are frequently liable to the most unaccount-
able accidents. Indeed, it is much to be lamented,
that so elegant and useful a process should be so
extremely delicate and uncertain.
It being necessary to hold the plate in a slanting
direction, in order to drain off the superfluous fluid,
there will naturally be a greater body of the liquid
at the bottom than at the top of the plate. On this
account, a grain laid in this way is always coarser
at the side of the plate that was held lowermost.
The most usual way is, to keep tlie coarsest side for
the fore-ground, that being generally the part
which has the deepest shadows. In large land-
scapes, sometimes various parts are laid Avith dif-
ferent grains, according to the nature of the subject.
The finer tlie grain is, the more nearly does the
impression resemble Indian-ink, and the fitter it is for
imitating drawings: but very fine grains have several
disadvantages; for they are apt to come off before
the aqua fortis has lain on long enough to produce
ENGRAVING IN AQUA TINTA. 439
the desired depth ; and as the plate is not corroded
so deep, it soon wears out in printing; whereas
coarser grains are firmer, the acid goes deeper, and
the plate will throw off a great many more impres-
sions. The reason of all this is evident, when it is
considered, that in the fine grains, the particles are
small and near each other, and consequently the
aqua fortis, which acts laterally as well as down-
wards, soon undermines the particles, and causes
them to come off. If left too long on the plate,
the acid would eat avvay the grain entirely.
On these accounts, therefore, the moderately
coarse grains are more sought after, and answer
better the purpose of the publisher, than the fine
grains which were formerly in use.
Although there are considerable difHculties in
laying properly the aqua tint grain, yet the corrod-
ing the copper, or biting-in, so as to produce ex-
actly the tint required, is still more precarious and
uncertain. All engravers allow that no positive
rules can be laid down, by which the success of
this process can be secured ; nothing but a great
deal of experience and attentive observation can
enable the artist to do it with any degree of cer-
tainty.
There are some hints, however, which may be
of considerable importance to the person who
wishes to attain the practice of this art. It is evi-
dent, that the longer the acid remains on the cop-
per, the deeper it bites, and consequently the
darker will be the shade in the impression. It
may be of some use, t'lerefore, to have several bits
of copper laid with aqua tint grounds, of the same
kind to be used in the plate, and to let the aqua
fortis remain for different lengths of time on each ;
and then to examine the tints produced in one,
F F 4
440 ENGRAVING IN AQUA TINTA.
two, three, four minutes, or longer. Observations
of this kind, frequently repeated, and with diifer-
ent degrees of strength of the acid, will at length
assist the judgment, in guessing at the tint which
is produced in the plate. A magnifier is also use-
ful to examine the grain, and to observe the depth
to which it is bit. It must be observed, that no
proof of the plate can be obtained till the whole
process is finished. If any part appears to have
been bit too dark, it must be burnished down with
a steel burnisher ; but this requires great delicacy
and good management not to make the shade
streaky ; and as the beauty and durability of the
grain is always somew^hat injured by it, it should
be avoided as much as possible.
Those parts which are not dark enough must
have a fresh grain laid over them, and be stopped
round with varnish, and subjected again to the
aqua fortis. This is called re-biting, and requires
peculiar care and attention. The plate must be
very well cleaned out with turpentine before the
grain is laid on, which should be pretty coarse,
otherwise it will not lay upon the heights only, as
is necessary, in order to produce the same grain.
If the new grain is different from the former, it
will not be so clear nor so firm, but rotten.
We have now given a general account of the
process of engraving in aqua tint, and we believe
that no material circumstance has been omitted,
that can be communicated without seeing the
operation ; but after all it must be confessed, that
no printed directions whatever can enable a person
to practise it perfectly. Its success depends upon
so many niceties, and attention tp circumstances
apparently trifling, that the person who attempts
it must not be surprised if he does not succeed at
ENGRAVING IN AQUA TINTA. 441
first. It is a species of engraving simple and ex-
peditious, if every tiling goes on well ; but it is
very precarious, and the errors which are made are
rectified with great difficulty.
It seems to be adapted chiefly for imitation of
sketches, washed drawings, and slight subjects j
but does not appear to be at all calculated to pro-
duce prints from finished pictures, as it is not sus-
ceptible of that accuracy in the balance of tints
necessary for this purpose. Nor does it appear to
be very suitable for book-plates, as it does not print a
sufficient number of impressions. It is, therefore,
not to be put in competition with other modes
of engraving. If confined to those subjects for
which it is calculated, it must be allowed to be
extremely useful, as it is expeditious, and may be
attained with much less trouble than any other
mode of engraving. But even this circumstance
is a source of mischiefj as it occasions the produc-
tion of a multitude of prints that have no other
effect than that of vitiating the public taste.
Engraving in aqua tint was invented by Le
Prince, a French artist, who kept his process a
long time secret, and it is said he sold his prints at
first as drawings J but he appears to have been
acquainted only with the powder-grain and the
common method of stopping-out. The prints
which he produced are still some of the finest
specimens of tlie art. Mr. Paul Sandby was the
first who practised it in this country, and it was
by him communicated to Mr. Jukes. It is now
practised very generally all over Europe j but no
where mor^ successfully than in this kingdom.
442
WOOD-CUTTING.
Wood-cutting or engraving on wood is a pro-
cess exactly the reverse to engraving on copper.
In the latter, the strokes to be printed are sunk,
or cut into the copper, and a rolling-press is used
for printing it ; but in engraving on wood, all the
wood is cut away, except the lines to be printed,
which are left standing up like types, and the
mode of printing is the same as that used in letter-
press.
The wood used for this purpose is box-wood,
which is planed quite smooth. The design is then
drawn upon the wood itself with black-lead, and
all the wood is cut away with gravers and other
proper tools, except the lines that are drawn. Or
sometimes the design is drawn upon paper, and
pasted upon the wood, which is cut as before.
This art is of considerable difficulty, and there are
few who practise it. It is, however, useful for
books, as the printing of it is cheaper than that
of copper-plates. It Cannot be applied equally
well to all the purposes to which copper-plate en-
graving is applicable.
ETCHING ON GLASS.
Glass resists the action of all the acids, except
the fluoric acid. By this, however, it is corroded
in the same manner as copper is by aqua fortis ;
and plates of glass may be engraved in the same
manner as copper.
There are several methods of performing this.
We shall first describe the mode of etching by
ETCHING ON GLASS. 443
means of the fluoric acid in the state of gas.
Having covered over the glass to be etched with
a thin coat of virgin-wax (which is only common
bees- wax bleached white,) draw the design upon
it, in the same manner as in etching on copper.
Then take some Jluoy^ spar, commonly called
Derhijshire spar, pound it fine, and put it into a
leaden vessel, pouring some sulphuric acid over it.
Place the glass with the etched side lowermost
over this vessel, two or three inches above it^
Apply a gentle heat to the leaden vessel ; this will
cause the acid to act upon the fluor spar, and dis-
engage the gas, W'hich will corrode the glass.
When it is sufficiently corroded, remove the wax
by oil of turpentine.
This etching may be also performed by raising
a margin of bordering-wax all round the glass,
in the same manner as on copper, and pouring
on the liquid fluoric acid, which acts upon the
glass. The method of making this acid was
described under the article fluoric acid, in che-
mistry.
A third method of etchino; on fflass is as follows :
Having put the wax on the glasSj draw your
design, and raise a margin all round it. Then
])ut pounded fluor spar, with some sulphuric
acid diluted with Vv'ater, upon the glass. The
sulphuric acid will disengage the fluoric, which
will be absorbed by the water, and corrode the
glass.
In all the above-mentioned methods, some of the
gas is let loose in the apartment, and is exceed-
ingly suffocating. To remedy this inconvenience,
an apparatus was contrived by the editor of this
work, some years ago, and is found to answer
perfectly.
444 ETCHING ON GLASS.
A, Fig. 5., Plate XVII., Vol. 1., is a cylindrical
leaden vessel, having a rim B all round it, made
like Count Rumfoid's steam rim for cooking
vessels, into which is put a little water. Into this
rim fits a cover c, having a pipe d coming from it,
Mhich is inserted into a large oblong vessel e of
sheet lead, or iron well tinned, having a rim and
cover similar to the vessel A, only the cover has no
aperture. The fluate of lime powdered and the
sulphuric acid are put into the leaden vessel A,
which is placed upon a stand made of wire, having
a lamp to heat the contents of the vessel over it.
As soon as the gas is evolved it ascends, and not
being able to escape through the rim B, on account
of the water, which condenses a portion, it pro-
ceeds through the tube into the large vessel e, in
which is placed, upon stands of wire, the glass
prepared for etching by drawing through a var-
nish, as above described.
In this vessel the gas collects, and acts upon the
glass : the rim with water prevents any noxious
fumes from escaping into the room. The vessel e
is placed upon a stand of such a height as to agree
with that of the lamp. In this manner the process
may be conducted with the utmost ease and
elegance.
Beautiful ornaments may thus be etched on
glass, and applied to decorate windows, by paint-
ing the figure of the ornament on panes of glass
with enrgravers' stopping varnish, and tlien ex-
posing the panes to the action of the gass in the
vessel e. The gas will corrode all the surface of
the glass, except where the varnish has been put,
and give it much tlie appearance of ground glass,
which may be rendered more or less opaque by
lengthening or shortening the process. The parts
ETCHING ON GLASS. 445
where the varnish was appUed will continue trans-
parent and seem extremely bright. It is to be
noticed, when the liquid fluoric acid is used, the
lines which have been etched continue still trans-
parent ; but when the gas has been employed, the
line is white and opaque, as if cut by a wheel.
LITHOGRAPHY.
This art is so called, because the impressions
are produced from drawings made on stone. It
was invented by Aloys Sennefelder, a German,
about the year 1800.
There are several styles of drawing employed in
lithographic prints. The chief are, the line manner,
and the chalk manner. In the line manner, which
is similar in its effect to the line engraving on cop-
per of second rate quality, lines are drawn on a
stone with a particular sort of ink, by means of
pens of various kinds, or a camels-hair pencil.
In both these methods, the same kind of stone is
used ; but in the line manner, the stone must be
polished smooth with pumice-stone, whereas, for
the chalk it is made a little rough, by grinding with
sand. The stone must be calcareous and of a light
colour. The white lias in this country answers
tolerably well, but is not so fit as the German
stones.
The lithographic ink is composed of equal parts
of tallow, bees-wax, shell lac, and common soap,
with a sufficient quantity of lamp-black to colour
it. These ingredients are mixed by heating them.
446 LITHOGRAPHY.
and even burning them in an iron vessel. When
cold, the mass is rubbed on a tile with water, like
Indian ink, and put into a pen or brush.
The lithographic chalk is formed of 2 oz. of tal-
low, 2|- oz. of bees-wax, 1 oz. of shell lac, and
If oz. of common soap. These are also united by
heating as before ; when cold it is cut into slips,
and used as a cravon.
When the drawing is made on the stone with
the pen and ink, or with the chalk or crayon, some
water, having in it a little nitric acid, is poured
over the stone, which slightly corrodes the sur-
face ; gum-water is then laid on with a brush, and
the stone is left to dry ; it is now ready for print-
ing from.
To print from the stone, the printer proceeds to
wet the surface of it with a sponge with w^ater,
and then applies the printing ink, by a roller.
The printing ink, made of equal parts of burnt
oil or varnish, and lamp-black, sometimes with the
addition of wax and tallow, adheres to the lines
which have been drawn wdth the lithographic ink
on the stone, while the water prevents it from
sticking to the rest of the surface. The lines alone
are thus charged with printing ink. Some damped
paper is now laid upon the stone, and passed
through a press, by v\^hich an impression is obtained.
The stone is again wetted, and the printing ink
applied for a second impression, and so on.
The process is the same for printing chalk draw-
ings ; but they are more difficult to print, and give
fewer impressions.
This art has made considerable progress on the
continent ; in this country it has advanced more
slowly, chiefly from the secresy employed in the
LITHOGRAPHY. 447
processes of printing. On this account, its advan-
tages were not well comprehended, it being difficult
to institute a just comparison between this and the
other species of engraving, which are in this coun-
try carried to such a high degree of perfection. It
is now, however, rapidly improving, since artists
have been induced to take it up, and we shall
probably soon' equal, if not surpass, our continental
neighbours.
INDEX.
Abstract
44-6
454^
of Mechanics, i.
of Hydrostatics, i.
-- ofPneumaticSji. 455
of Hydraulics, i.456
• of Acoustics, i. 458
of Optics, i. 459.
. of Electricity, i. 461
————— of Galvanism, i. 463
of Magnetism, i. 464
of Astronomy, i. 466
Acid Nitrous, ii. 44
Nitric, ii. 45
Hydro-chloric, or muri-
atic, ii. 65
— — Sulphurous, ii. 68
Sulphuric, ii. 69
Carbonic, ii. 70
Phosphorous, ii. 76
Phosphoric, ii. 76
Boracic, ii. 76
Fluoric, ii. 77
Fluo-boric, ii. 78
• Siliceo-fluoric, ii. 78
Arsenic, ii. 117
Arsenious, ii. 1 17
Molybdic, ii. 120
Chromic, ii. 126
— — Tunstic, ii. 120
Tartaric, ii. 133
-—, Oxalic, ii. 133
Malic, ii. 133
Gallic, ii. 134
VOL. II. G
Acid Citric, ii. 134
Benzoic, ii. 134
— — Kinic, ii. 134
Acetous, ii. 136
Acetic, ii. 137
Lactic, ii. 139
Uric, ii. 139
Amniotic, ii. 139
Saccho-lactic, ii. 140
Sebacic, ii. 140
Prussic, ii. 140
Formic, ii. 140
Adipocire, ii. 139
Affinity, chemical, ii. 5
Air, mechanical properties of,
i. 126 — weight of, 135 —
pressure of, 131 — density
of, 135 — height of, 135 —
elasticity of, 137 — con-
densed, 145
Air pump, i. 129 — experi-
ments with it, i. 139 — prac-
tical directions for using, i.
153
Air gun, i. 157
Air balloons, i. 162
Air atmospheric, chemical pro-
perties of, ii. 46
— fixed, ii. 71
Albumen, ii. 138
Alkalie.'j, ii. 78
Alkohol, ii. 135
Alum, ii. 92
Alumina, ii. 91
4.50
INDEX.
Amalgams, ii. 104-
Amber, ii. 129
Ammonia, ii. 85
Animal substances, ii. 137
AnimalculcE, method of pro-
curing, ii. 339
Antimony, ii. 11, >
Aquatinta, ii. 432
Arsenic, ii. 116
Arsenic acid, ii. 117
Astronomy, i. 413
Attraction, i. 12
•-, electrical, 1.324-
— , magnetic, i. 398
, chemical, ii. 4
Aurum musivum, ii. 325
B.
Balance, i. 32
Balloons, air, i. 162
Barometer, i. 147
Barometer gauge, i. 154
Barytes, ii- 89
Battery, electrical, i. 340
, galvanic, i. 383
Beer, ii. 135—153
Bellmetal, ii. 110
Bismuth, ii. 116
Bitter principle, ii. 139
Bitumen, ii. 130
Bleaching, ii. 160
Blood, ii. 140
Bone, ii. 140
Boron, ii. 76
Brass, ii. 110
Bread, manufacture of, ii. 147
Brewing, ii. 153
Bronze, ii. 110
BronzinsT, ii' 28*2
C.
Calico-printing, ii. 196
Calomel, ii. 104
Caloric, ii. 22
Camera obscura, i. 312
Carbon, ii. 70
Camphor, ii. 132
Carbonates, ii. 73
Carbonate of soda, ii. 82
. of ammonia, ii. 85
of lime, ii. 87
^ of magnesia, ii. 89
— of barytes, ii. 90
Carbonic acid, ii. 71
Carbonic oxide, ii. 73.
Carburets, ii. 73
Casts, method of making, ii.
289
Catechu, ii. 131—209
Caoutchouc, ii. 130
Cements, various kinds of, ii.
292
Centre of gravity, i. 20 — of
oscillation, i. 82
Centrifugal and centripetal
forces, i. 19
Cerium, ii. 124
Chemistry, definition of, ii. 1
• Animal, ii. 141
■ , instrumentsfor, ii.4
Chlorates, ii. 65
Chloric acid, ii. 64
Chlorides, ii. 65
Chlorine, ii. 63
Chromate of lead, ii. 113
Chromium, ii. 123
Chronometers, i. 83
Cinnabar, ii. 104
Clay, ii. 92
Clepsydra, i. 83
Clocks, i. 84
Cobalt, ii. 119
Colouring matter, ii. 131
Colouring used for drawing,
ii. 410
Columbium, ii. 124
Combination, chemical, ii. 6
Comets, i. 439
Compass, mariners', i. 402 —
411
, azimuth, i. 412
9
INDEX.
451
Condenser for air, i. ItS Crayon painting, ii. 409
Copal, ii. 129 — method of Cupellation, ii. 215
dissolving it, ii. 24'3 Currying, art of, ii. 211
Copper, ii. 109 Cyanogen, ii. 74
Cotton, bleaching of, ii. 170
D.
Dip, of the magnetic needle,
i. 403
Discharge, electrical, i. 339,
345
Distillation, ii. 8.
Diving bell, i. 159
Divisibility of matter, i. 2
Drawing, "ii, 342—348
--, implements for, ii.342
— , the figure, ii. 388
— , landscapes, ii. 400
•, mechanical, if. 403
Drawings, methods of copying,
ii. 404
Dyeing, ii. 178
E.
Earth, considered as a planet,
i. 433
Earths, ii. 86
Echo, i. 229
Eclipses, i. 441
Elain, ii. 139
Electricity, i.319 — considered
chemically, ii. 35
, atmospheric, i. 346
• , miscellaneous ex-
periments in, i. 352
, animal, i. 373
, medical, i. 375
Electrometer, i. 326
Electrophorus, i. 344
Elementary substances, ii. 2
Engraving, ii. 419
Epsom salt, ii. 89
Equator, i. 415
Etching on copper, ii. 423
— — — on glass, ii. 442
Ether, ii. 136
Euchlorine, ii. 64
Evaporation, ii. 8
Extension, i. 5
Eye, description of, i. 249
Fecula, ii. 127 — 148
Fermentation, ii. 134 — 150
Fibrin, ii. 138
Filtration, ii. 7.
Fine arts, ii. 342
Fireworks, artificial, ii. 329
Flax, ii. 161
Fluidity, i. 6
Fluates, ii. 78
F'luoboric acid, ii. 78
Fluoric acid, ii. 77
Fluorine, ii. 77
Fluor spar, ii. 77
Fly wheels, i. 62
Fountain, i. 178
Friction, i. 57
F\dling, ii. 172
Fulminating powder, ii. 321
Furnaces, ii. 18
Galvanism, i. 381
Gas, ammonical, ii. 85
Gas, definition of, ii. 26
G.
Gelatine, ii. 137
Geometry, practical, ii. 348
Gilding, ii. 261
G G 2
452
INDEX.
Glass, chemical composition, Gold, ii. 99
ii, 91 — manufacture of, ii. Gravity,!, l^ — specific, i. 117
235 Grottoes, artificial, ii. 330
Glauber's salts, ii. 83 Gum, ii. 126
Glucine, ii. 93 Gunpowder, composition of, 82
Glue, ii. 292 Gypsum, ii. 88
Glutin, ii. 128—148
H.
Hair-rope machine, i. 195
Harmony of sound, i. 228
Hops, ii. 157
Hydraulics, i. 176
Hydrocarbonate gas, ii. 59
Hydrocyanic acid, ii. 74'
Hydrogen, ii. 4'9— an acidifying
principle, 54?
Hydrometer, i. 120
Hydrostatics, i. 106
Hydrostatic balance, i. 118
Hydrostatic bellows, i. Ill
Hydrostatic paradox, i. 109
Hygrometer, 15 i. 2
L
Japanning, li. 248
Impenetrability of matter, i. 2
Inclined plane, i. 43
Ink, method of making, ii. 306 Iridium, ii. 121
— , sympathetic, ii. 308 Iron, ii. 104 — ores of, 106
Ink, Indian, ii. 346
Iodine, ii. 66
Invisible girl, i. 230
Kelp, ii. 213—235
K.
L.
Lac, ii. 129
Lacquering, ii. 258
Landscapes, drawing of, ii. 400
Lead, ii. Ill
Leather, nature of, ii. 201 -^
tanning of, ii. 202
Lever, i.24
Light, velocity of, i. 232 — •
refraction of, 234 — con-
sidered chemically, ii. 33
Lens, i. 236 — burning, i. 240 —
focal distances of, 243
Lime, ii. 87
Linen, bleaching of, ii. 160
Lithia, ii. 84
Lithography, ii. 445
Lixiviatio%ii. 8
Loadstone, ii. 105
Lute, used in chemical ope-
rations, ii. 9. 304
N.
Narcotic principle, ii. 1 32
Nickel, ii. 117
Nitrates, ii. 46
Nitrate of potash or nitre, ii.
81
Nitric acid, ii. 45
INDEX.
453
Nitric oxide or nitrous gas, ii.
43
Nitrogen, ii. 39
Nitrous acid gas, ii. 44
Nitrous acid, ii. 44
Nitrous oxide, ii. 40
Nomenclature of chemistry, ii.
19. 142
M.
Machines, compound, i. 48
Machine, electric, i. 322
Magic lanthorn, i. 316
Magnesia, ii. 89
Magnetism, i. 396
Malt, 135—154.
Manganese, ii. 118
Mastic, ii. 129
Matter, i. 1 — its proper-
ties, i. 2
Mechanics, i. 1
Mechanic powers, i. 23
Mercury, ii. 103
Metals, ii. 94 — refining of,
ii. 215.
Mezzotinto scraping, ii. 431
Microscopes, i. 271
Milk,ii. 139
Mills, i. 67
Mirrors, i. 262
Mixture, as distinguished from
combination, ii. 6
Mobility of matter, i. 2
Molybdena, ii. 120
Moon, i. 436
Mordant, ii. 180
Motion, laws of, i. 7 — commu-
nication of, i. 58 — regula-
tion of, by fly wheels, i. 62
Moving powers, i. 52
Moulding and casting, ii. 284
Mucilage, or gum, ii. 126
Mucus, ii. 138
Multiplying glass, i. 311
Muriate of soda, ii. 83
of ammonia, ii. 86
Muriatic acid, ii. 65
0.
Oil of vitriol, ii. 69
Oil, fixed, ii. 128
volatile, ii. 129
animal, ii. 139
phosphoric, ii. 319
Operations, chemical, ii. 6
Optics, i. 232
Orrery, electrical, i. 333
Osmium, ii. 121
Oxychloric acid, ii. 64
Oxydes, ii. 96
Oxygen, ii. 36
Oxygenated muriatic acid,
used in bleaching, ii. 166
Oxynmriate of potash, ii. 82
P.
Palladium, ii. 122
J'aper, bleaching of, ii. 177
Paradox, hydrostatic, i. 109
Paste,method of making, ii.303
Pasting, ii. 218
Pearlash, ii. 80
Pendulum, i. 80
Perkinism, i. 394
Perspective, ii. 374 ^
Pewter, ii. Ill
Phantasmagoria, i. 316
Phlogiston, ii. 98
Phosphorus, ii. 74— method of
making, ii. 316
Phosphoretted hydrogen, ii. 62
l^hosphoric acid, ii. 76
Phosphuret of lime, ii. 88. 320
Pinchbeck, or princes' metal,
ii. 110
Plaster of Paris, ii. 89
1-54
INDEX.
Plating, ii. 276
Planets, i. 422 — 437
Points, electrical, i. 331
Polarity of the magnet, i. 101
Potash, ii. 79.
-^ , manufacture of, ii. 214
Potassium, ii. 81
Pottery, ii. 228
Precipitation, chemical, ii. 5
Press, Bramah's, i. 115
Prussian blue, ii. 74
Prussic acid, ii. 74.
Pulley, i.41.
Pump, air, i. 129 — sucking, i.
183— lifting, i. 185 — forc-
ing, i. 186 — various con-
structions of, i. 188
Pyrometer, ii. 30
R.
Recapitulation of the principal
tacts in vol. i. 446
iteceipts, miscellaneous, ii. 316
Reflection of light, i. 261
Refining metals, ii. 215
Refraction of light, i. 234-247
Repulsion, i. 22
, magnetic, i. 400
Resin, ii. 129, 239 — animal re-
sins, ii. 140
Retorts described, ii. 9
Rhodium, ii. 121
Ribbands covered with gold by
a chemical process, ii. 325
Rupert's drops, ii. 238
S.
Sacchrometer, ii. 157
Saltpetre, ii. 81
Scapement, i. 86
Screw, i. 45
Sea salt, composition of, ii. 83
Selenium, ii. 125
Shock, electrical, i. 335
Silica, ii. 90
Silks, bleaching of, ii. 173
Silver, ii. 101
Silvering, ii. 275
Size, method of making, ii. 304
Soap, chemical composition of,
ii. 84. 128
Soda, ii. 82 — manufacture of,
ii. 212
Sodium, ii. 83
Soldering, ii. 283
Solidity of matter, i. 2.
Sound i. 227
Spark, electric, i. 328
Speaking tubes, i. 230
Specific gravities, i. 1 17 — table
of, i. 122
Spectacles, i. 257
Spermaceti, ii. 139
Spouting of water, i. 176
Springs, nature of, explained,
i. 116
Staining wood, ii. 313
of ivory, ii. 316
Stains, method of removing,
ii. 310
Starch, ii. 127
Stars, fixed, i. 439
Statera, i. 35
Steam engine, i. 206 ■ — inven-
tion of, 207 — Savary's, 208
— Newcomen's,211 — Watt's,
216 — Cartwright's, 224 —
Highpressure, 224
Steam boats, i. 225
Steam used in bleaching, ii. 169
Stearin, ii. 139
Steel, ii. 105 — a method of
making, 337
Strontia, ii. 90
Suction, i. 133
Sugar, ii. 127 — animal sugar,
ii. 140
Sulphate of lime, ii. 89
■ of magnesia, ii. 89
INDEX.
4.55
Sulphate of barytes, ii. 90
of iron, ii. 105
of copper, ii. 19
of soda, ii. 83
Sulphur, ii. 67
Sulphuretted hydrogen, ii. 61
Sulphuric acid, ii. 69
Sulphuring in bleaching, ii. 172
Sun considered as the centre of
our system, i. 431
Syphon, i. 179
T.
Tannin, ii. 131
Tanning, ii. 201
Telescope, i. 297
, refracting, i. 297
, binocular, i. 301
, reflecting, i. 303
, acromatic, i. 308
Terella, i. 405
Thorina, ii. 93
Tides, cause of, i. 444
Time keeper, i. 84
Tin, ii. Ill
Tinning, ii. 281
Titanium, ii. 123
Tobacco-pipes, manufacture
of, ii. 234
Tombac, ii. 110
Torricellian vacuum, i. 129
Touch, magnetic, i. 406
Transparencies, method of
making, ii. 407
Trumpet, speaking, i. 231 —
hearing, i. 231
Tungsten, ii. 120
u &v.
Uranium, ii. 124
Vacuum Torricellian, i. 129
Boylean, i. 129
Valves, i. 202
Varnishing, ii. 239
Vegetable substances, ii. 125
Verdegris, ii. 110
Vision, cause of, i. 244
W.
Watches, i. 84 — 89
Water, chemical constituents
of, ii. 54
Water-spouts, i. 175
Wax, ii. 132
Weatlier-glass, i. 150
Wedge, i. 44
Wheel and axis, i. 36
Wheels, bevelled, i. 60
Wheels carriages, i. 101
Wind gauge, i. 152
Winds, various classes of, i. 172
Wood-cutting, ii. 443
Woody fibre, ii. 131
Wool, bleaching of, ii. 171
Zenith, i. 415
Zinc, ii. 114
Z.
Zirconia, ii. 93
Zodiac, i. 419
THE END.
London:
Prluted by A. & R. Spottlswoode,
New-Street-Sqiiare.
CHEMISTRY.
Piatt I.FolJI.
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