DISTILLATION. 
hoi, and the various essential oils, is called 
a still. It is chiefly made of copper, and 
ought to be so constructed, that as great 
an evaporable surface as possible may be 
exposed. Those employed in the Scotch 
distilleries are in the form of an erect cone, 
the base of which is about four times the 
altitude. The vapour which comes from 
the still, is condensed in two ways. Tiie 
first is the oldest and most simple method, 
but not the most effective. The- head, or 
capital of the still is so formed, as to have 
a vessel or cavity on the outside, contain- 
ing cold water ; the inside is in the form 
of a cone, and sometimes of a dome, round 
the base of which is placed a channel, ter- 
minating in an inclined beak, or tube, to 
convey the liquid arising from the con- 
densed vapour. When the vapour rises up 
against the conical, or dome like surface, 
the external water causes it instantly to 
condense, and the drops inn down the sur- 
face into the channel, from whence they 
pass into the delivering tube, and thence 
into the receiver. The other method of 
condensation, consists in letting the vapour 
pass through a spiral tube, fitted into the 
inside of a tub, which is filled with cold 
water, and so contrived, that the product 
of the distillation shall have no communi- 
cation with the external water. This, tub, 
which is called a worm tub, should be sup- 
plied with cold water at the bottom, while 
the warm water, caused by the condensa- 
tion of tire vapour, should be made to run 
off at the top. 
The apparatus employed for distilling 
bodies more easily condensible, consist of 
two parts, one called the retort, contain- 
ing the substance to be distilled, and the 
otlier the receiver, because it receives the 
substance raised from the retort. In the 
disti^ation of bodies which afford perma- 
nent gases as well as condensible matters, 
in addition to the receiver, a number of 
connected vessels are employed, constitut- 
ing what, from its inventor is called a 
Woulfe’s apparatus, in which, what is not 
condensed, or absorbed in the first bottle, 
passes forward to the second, and so on to 
the third and fourth, till at length tlfe ab- 
solutely incondensable part is received 
into a vessel called a gasometer. Before 
the invention of this apparatus, this kind 
of distillation was attended with great dan- 
ger, both to the apparatus and the opera- 
tor; tlie receiver being very liable to 
burst, and the fumes being intolerably suf- 
focating. Both these inconveniences are 
completely obviated by the invention of 
the Woulfe’s apparatus. Sometimes an ap- 
paratus called an alembic is used for dis- 
tillation ; it is generally of glass, and is used 
for experiments in the small way ; it con- 
sists of a bottle holding the substance to 
be distilled, having a dome like head, fur- 
nished with a channel similar to that of the 
common stile; indeed it differs only from 
it, in not having cold water on the outside. 
There are various modes of applying heat 
in distillation, depending upon the nature 
of the apparatus employed, as well as upon 
tire substance to be distilled. The com- 
mon still, wdiich being of metal, is imme- 
diately exposed to the naked fire, since 
from its tenacity, and its property of con- 
ducting heat with facility, it is not liable to 
crack, which is not the case with glass and 
earthen w^are. If the vessel helding the 
substance to be distilled, be of the latter 
kind, it is essential to apply the heat very 
gradually and uniformly, and after the pro- 
cess, to suffer it to cool in a similar manner. 
This is effected in different ways ; the most 
common of which is the sand bath, which 
consists of a vessel of iron filled with fine 
dry sand. The retort, or other vessel, is 
imbedded in the sand previous to tire ap- 
plication of the fire ; the inferior conduct- 
ing power of the sand does not allow the 
heat to approach the retort, but in that 
gradual way, which, will insure its safety 
from cracking. The heat must also be 
more uniform, since any sudden increase, 
or diminution of the fire, will not so imme- 
diately affect the retort. 
In experiments in the small way, the 
lamp will answer every purpose of the sand 
bath, as the sliding rest containing the re- 
tort, admits of its being placed at any given 
distance from the flame. In addition to 
this, the Argand lamp can be adjusted by 
the rack, to, almost any degree of intensity 
below its maximum. Another method of 
defending the retort from the too rapid 
effect of the heat, consists in coating the 
outside with a mixture of horse-dung and 
clay, or loam. When a limited degree of 
heat is required in distillation, recourse is 
had to a bath of some liquid, ^ whose boil- 
ing point will give the degree of heat re- 
quired, such as water, oil, or mercury. If, 
for instance, it were required to separate 
any substance from water more volatile 
than that liquid, it would be necessary to 
employ a water- bath, in which to place 
the retort, keeping the water in the bath 
below its boiling point. 
