I quantity thrown out is exactly ascertained : 
I t his rod is so divided us to express the con- 
I tents of the inner vessel in cubic feet, kc. 
■ This instrument also answers for' breat I ling 
lany of the gases, by applying a mouth-piece 
I to the cock. To render it more portable, 
[the weights gg are sometimes included in 
the uprights ii, which are hollow and wide 
lenouga to receive them. Sometimes also 
I there is another branch from the bottom of 
[ the pipe, in the middle, directed to the side 
I of the other cylinder, and coming upwards 
I by the side to the top, where there is another 
", cock attached. 
Crystallization. — When a salt is dissolved 
in water, or other fluid, and by evaporation 
the fluid is driven off, the salt gradually ac- 
quires the solid form, and n doing this, it ar- 
ranges its particles in a particular manner; 
\ some salts arrange themselves in the form of 
[pyramids, some of prisms of different kinds, 
l&c. Vessels of earthenware, or glass, are 
employed for such crystallizations. They 
j must be placed where they are perfectly still, 
land well defended from dust or accidents. 
Solution. — Whenasalt is mixed with water, 
it loses its state of solidity ; the particles of salt 
are divided and unite themselves to those of the 
water, forming a liquid, of which all the parts 
are homogeneous, or of the same kind. The 
[same takes place when resin is mixed with 
jspirits of wine. In this process neither the 
(salt nor the water is decomposed ; and the 
'salt may be recovered agayi in its original 
state and quantity, by driving off the water by 
evaporation. 
| T he dissolution of metals by acids, how- 
ever, is of a different nature: here, either 
the metal, the acid, or the water, is altered, 
find different products are obtained. Ves- 
sels of glass are generally used for solutions 
pnd dissolutions. The liquid used for dis- 
solving a metal, or other solid substance, is 
usually called a solvent, or menstruum. 
| Precipitation. — The recovery or separa- 
tion of a body from its solvent, by the addi- 
tion of a third substance, so that the former 
pray re-appear m a solid state, however di- 
vided, is called precipitation. The substance 
thus recovered, is called a precipitate, and the 
super-added body that occasions this precipi- 
tation is called a precipitant. 
! Fusion. — The melting, or causing any 
body to pass from the solid to the liquid state, 
|y the action of fire, is called fusion. The fu- 
sion of metallic substances requires vessels suf- 
ficiently strong to resist the fire. These ves- 
jels 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- 
iibles, and are generally of the forms repre- 
sented fig. 8 ; sometimes these vessels have 
'overs made of earthenware ; but sometimes 
she fused metal must be exposed to a current 
)f air. In that case the crucibles are 
[road and shallow, as at fig. 9. These are 
jailed cupels ; and they are formed of cal- 
cined bones, mixed with a small quantity of 
flay, or of a mixture of clay and black-lead 
jowder. But the cupels must not be placed in 
[closed furnace, or be surrounded by coals ; 
br, in that case, the required current of air 
puld not have access to the fused metal, 
they are therefore placed under a sort of 
fven of earthenware, which is called a muf- 
je, as represented tig. 10; which, with the 
pcluded cupel, is exposed to the heat of a 
Brua.ce, 
CHEMISTRY. 
[ Furnaces. — In the application of the action 
i of heat to bodies, furnaces of different forms 
are employed, according to the operations 
for which they are destined. A furnace is a 
kind of hollow cylindric tower, A BCD 
(Jig. II); sometimes a little wider at the 
top, with notches in, m, in, to give a passage 
to the air. This furnace ought to have a 
least two lateral apertures ; an upper one F, 
which is the door of the fire-hole II ! ; and a 
lower one G, which is the door of the ash- 
hole C 1). In the interval between these two 
doors the furnace is divided into two parts 
by a horizontal grate, destined to support the 
charcoal. r I he place occupied by this grate 
is indicated by the line IT 1 ; above the grate 
is the fire-hole where the fire is maintained ; 
and below it is the ash-hole, where tire ashes 
are collected as they are formed. 
Another kind of furnace often necessary, is 
that called the reverberating furnace (fig. 12) ; 
it consists of an ash-hole IT 1 K L, a fire-hole 
K L M N, a laboratory M N 11 R, and a dome 
R RfSS ; above the dome is a tube TT V V, 
to which several more can be added if re- 
quired. In the laboratory is placed a retort, 
which is supported by two iron bars that run 
across the furnace ; the neck of it passes 
through the lateral aperture O, and has 
adapted to it a receiver. As a strong heat is 
sometimes required for this furnace, a large 
volume of air must be made to pass through 
it ; and in that case a great deal of heat is 
disengaged. For this reason, instead of one 
aperture to the ash-hole, there must be two: 
when only a moderate heat is required, one 
of them may be shut ; if a strong heat is ne- 
cessary, they may be both opened. It will 
be of advantage also to make the upper aper- 
ture TT of the dome pretty large. The use 
of the dome is to reverberate the heat and 
flame on the retort, in order that it may 
every where be exposed to nearly an equal 
heat ; by which means the vapours can be 
condensed only in the beak of the retort and 
in the receiver, and are also forced to pro- 
ceed thither. When matters which do not 
require a strong degree of heat are to be 
fused, the reverberating furnace may be em- 
ployed as a fusing furnace. The laboratory 
MNllR in that case is removed ; and the 
dome IIRSS is placed on the fire-hole MN, 
as represented. 
One of the best fusing furnaces ever made, 
is that constructed by Lavoisier, and which is 
represented fig. 13. ” The following is the de- 
scription which he gives of it in his Elements 
of Chemistry. This furnace is in the form 
of an elliptical spheroid ABCD, cut off at 
the two ends by two planes which pass per- 
pendicular to the axis through the foci of the 
ellipse. From this shape it is capable of con- 
taining a considerable quantity of charcoal, 
while it leaves sufficient space in the intervals 
for the passage of the air. That no obstacle 
may oppose the free access of external air, it 
is perfectly open below, and stands upon an 
iron tripod. The grate is made of flat bars, 
set on edge, with considerable interstices be- 
tween them. To the upper part A B is added 
a chimney, or tube of baked earth, eighteen 
feet long, and equal in width to nearly half 
the diameter of the furnace. Lavoisier re- 
commends, as a thing of importance, to make 
the tube FG AB as bad a conductor of heat 
as possible ; it must therefore be constructed 
neither of iron-plate, nor of copper, as is 
commonly the case. 
333' 
AiyTher kind cf furnace is that necessary 
for assaying. In this furnace tnfc metal must, 
at the same time, be exposed to the most vio- 
lent heat ; and, secured from the contact of 
the air, become incombustible by its passage 
through the coals : on this account it lias been 
called the assaying or cupelling furnace. It 
is generally of a square form (fig. 14) ; and, 
like the other furnaces, has an ash-hole 
A ABB, a fire-hoic BBCC, a laboratory 
CCi)l), and a dome I)D L E. The labo- 
ratory is destined for receiving the muffle, 
which is a kind of small oven (fig. 10) made 
of baked earth, and close at the bottom. It 
rests on bars which traverse the furnace ; and 
being adjusted to the door of the laboratory,, 
is luted in with clay. It is in this small oven 
the cupels are placed, and the muffle is sur- 
rounded with charcoal : that above it being 
conveyed through the door 1 of the dome ; 
and that below it, through the door K of the 
fire-hole. The air which enters through the 
apertures of the ash-hole, after having served 
for the purposes of combustion, escapes 
through .the upper aperture E E of the dome.. 
In regard to the muffle, the air penetrates to 
it through the door G, and promotes the oxi- 
dation of the metal. T his furnace, however,, 
is attended with the following inconvenience:., 
if the do :r G of the laboratory is shut, the 
oxidation, for want of air, takes place slowly ; 
while, on the other hand, if it is open, the 
current of cool air causes the metal to be- 
come fixed, and retards the .operation. To- 
obviate this inconvenience, hot air should be 
conveyed to the muffle from without, by 
causing it to pass through an earthen tube,, 
kept in a state of ignition by the furnace it- 
self; and thus the interior part of the muffle 
would never become cold. 
A very useful kind of furnace is that in- 
vented by Dr. Black. It consists (fig. 15) of 
a cylindrical or elliptical body of. -sheet iron, 
coated within with a mixture of loam and 
clay. The aperture X at top is closed occa- 
sionally 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 (he chim- 
ney 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 substance 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, as fig. 16. 
T he blow-pipe contrived by Dr. Black, of 
a conical form, represented in fig. 17, is the 
most convenient : a is the nozzle. 
Of simple substances . — The object of che- 
mistry, in subjecting to experiment the dif- 
ferent bodies in nature, is that we may there- 
by be enabled to examine separately the 
substances which enter into their composi- 
tion. This science lias, during the last thirty 
years, made a very rapid progress. Formerly, 
oil and salt, as well as water, were considered 
as elementary bodies : now it is ascertained 
that they are compound substances. Saits, 
as we shall hereafter see, are composed of an 
ac id with some base, and their neutral state is 
the result of this union. Acids again are 
forpted by the combination of an acidifying 
principle (oxygen) which rs common to all, 
and a radical peculiar to each particular 
acid. See Acid. The radicals of the acids 
are not always simple substances: they are • 
