332 
venient substance for making (litres for che- 
mical 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 
©f the fluid when poured into it. 
Decantation is often substituted instead 
of filtration, for separating solid particles 
Which are diffused through liquors. These 
are allowed to settle to the bottom, and the 
clear fluid is geptlv poured off. If the sedi- 
ment is extremely light, and apt to mix again 
with the fluid, by the slightest motion, a 
syphon is used for drawing off the clear 
fluid. 
Lixiviation 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 
day, &c. the given body being broken to 
powder, is placed in water, which will dis- 
solve the salt, and keep it suspended, whilst 
the earthy matter falls to the bottom of (he 
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 
in less volatile. 
Simple evaporation is used when the more 
volatile or fluid substance is not to be pre- 
served. Various degrees of heat are em- 
ployed for this purpose, according to the na- 
ture of the substances. It is performed in 
vessels of wood, glass, metal, porcelain, &c. 
Basons made of WedgowOod’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, 
whi ch is then called a sand-bath. This af- 
fords a more regular degree of heal, and 
renders the vessels less liable to be bro- 
ken. 
When the fluid which is evaporated must 
be preserved, then the operation is called dis- 
tillation. 
Distillation is evaporating in close vessels, 
when we wish to separate two fluids of dif- 
ferent degrees of volatility, and to preserve 
the most volatile, or both of them. The sub- 
stance to be subjected to distillation, is put 
into some vessel that will resist the action of 
heat, called a retort, an alembic, or a still ; 
having a beak or neck projecting from it, 
to which is attached auotber vessel, to receive 
the fluid that rises first, which is called the re- 
ceiver. 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 conden- 
sation is sometimes assisted by making the 
vapour pass through a tube which is 
immersed in a vessel containing cold water. 
A (fig. 1, Plate) represents a retort used 
for distillation. It is a vessel, either of glass or 
baked earth, for containing the liquid to be dis- 
tilled. When it has a smajl neck, a, with a 
stopple fitted to it, for introducing the ma- 
terials through, it is called a tubulated retort. 
B is the receiver for condensing the vapour j 
which is raised, and into which the neck of j 
the retort is inserted. The joining, b, is made } 
air-tight by means of some substance applied j 
to it, "called a lute. Various methods are used j 
fbr supporting both the retort and receiver, j 
CHEMISTRY. 
according to the degree of heat employed in 
the process, and several other circumstances. 
See Lute. 
When great heat is employed, earthen re- 
torts are used, which are placed on or in the 
(ire. When a less heat is wanted, glass re- 
torts are generally employed; which must not 
be placed immediately on the (ire, unless 
they are coated over with a composition of 
clay and sand, which is 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 receiver is 
placed upon some stand convenient for the 
purpose, with a ring made of hay under 
L 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 va- 
pour, is condensed in the alembic, and falls 
into a groove all round Its inside, whence 
itn-uns out by the spout C, into the receiver 
Fig. 3, are conical tubes that fit into one 
another, for lengthening the necks of retorts, 
&c. to connect them with the receivers at 
any distance : they are called adopters. 
Fig. 4, are phials with bent glass tubes 
fitted hi them, for disengaging gases, and si- 
milar experiments. 
Fig. 5, represents an improved chemical 
apparatus, such as is used by Mr. Davy in 
his experiments at the Royal Institution. 
A is a japanned tin vessel, filled within two or 
three inches of the top with water. Just below 
the surface of the water is fixed a shelf having 
several holes bored through it, to which small 
funnels are attached underneath. The glass 
receiver B, intended to receive the gas, is 
filled with water; and being inverted with its 
mouth under water, it is raised up gently, and 
placed upon the shelf over one of the holes, 
w here it will remain full of water, which is 
kept up by the pressure of the atmosphere in 
the same way as the mercury is retained in 
the tube of the barometer. The material 
from which the gas is to be disengaged is put 
into the retort G, which is put through, and 
suspended in one of the rings of the lamp 
furnace Di E is an improved Argand’s lamp, 
having two concentric wicks, placed on the 
shelf F. The shelf is moveable up and down 
to bring the lamp to a convenient distance 
from the retort. The lamp is to be lighted, 
and as soon as the substances in the retort 
act upon each other sufficiently, the gas will 
begin to be disengaged, and will ascend 
through the hole in the shelf into the vessel 
B, and displace the water with which it had 
been filled. When the water is displaced, 
the receiver is full of gas which was disen- 
gaged from the retort, and may be preserved 
in it by keeping its mouth always under water 
in the cistern. This gas may he transferred 
from the vessel B to an)' other, in the follow - 
ing manner : Fill the vessel into which the gas 
is tq be transferred with the fluid in the trough, 
and place it on the shelf 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 depress- 
ing its^ottom, and elevating its mouth, so as 
to bring it more to a horizontal position, the 
gas ffi 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. 
If the oxyd of manganese is put into the 
retort G, and the lamp applied to it, great 
plenty of oxygen gas will escape from the 
retort, and will fill the receiver B. 
When the gas to be procured is absorb- 
able by water, quicksilver is used instead of 
w ater, and a much smaller vessel than A is 
made use of, which is generally made of wood 
or stone. A small glass vessel, capable of 
containing an ounce measure, is used for 
measuring gases; for if this phial is succes- 
sively filled and inverted under a large jar, we 
may thereby throw into that jar any required 
quantity of an elastic fluid, and as much of 
another as we please. 
G (fig. *5) is a strong glass graduated tube, 
for receiving a mixture of gases that are to 
be exploded by the electric spark. Near the 
closed end two wires pass through the glass, 
and almost touch each other : they are ce- 
mented in, so as to make the holes air-tight. 
Gases may be introduced into this tube ; and 
if the interval between the two wires is made 
a part of the electric circuit, by putting 
chains connected with a Leyden phial to the 
rings of the wires, the spark will pass through 
the interrupted space betw een the two wires, 
and explode the gases. 
A (fig. 6) is a glass retort, the beak of 
which is adjusted to a double tubulated bal- 
loon B. To the upper opening of the balloon is 
fitted a glass tube C, the other extremity of 
which is conveyed into the liquor contained 
in the glass vessel D : with this are connected 
two or three, or more similar vessels, by 
means of glass tubes, and to the last tubulure 
of the range of vessels i$ adapted a glass 
tube which is conveyed under a receiver 
placed upon the shelf of the pneumatic cis- 
tern. A (fig. 5). 
Water is poured 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 well 
fluted. By this method the purest and most 
concentrated products are obtained ; be- 
cause the water, which is always the re- 
ceiver, becomes saturated with them. In this 
way the common muriatic acid, the oxygenat- 
ed muriatic acid, volatile alkali, &c. &c. may 
be made in the best manner. 
Large vessels for containing air, and expell- 
mg any given quantity, are called gazometers. 
They are of various constructions ; one of 
the best is the following : A B ;fig. 7) 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 com- 
municate w ith the cock D. W ithin this ves- 
sel there is another cylindrical vessel, 
generally of glass, of smaller" size, F, open 
at bottom ; which is inverted and suspended 
by the lines ee, which go over the pulleys 
f,f,f, f, and have weights gg, attached to 
them, to balance the vessel F. While the 
cock D remains shut, if the vessel F is 
pressed downwards, the air included within 
it will remain in the same situation, on the 
principle of the diving-bell ; but if the cock 
is opened, and the vessel F is pressed down, 
the air included within it will escape through 
the cock ; and if a blow-pipe is attached to 
tlris cock, a stream of the gas may be thrown 
upon lighted charcoal, or any other body. 
By means of the graduated rod 1), also, the 
