from them a noxious impregnation, are distilled from gl: 
sels. The retort, or conical bottle bent nearly at a right angl 
used for this purpose: the heat being communicated to it by the me- 
dium of a sand-bath. The vapor is condensed in a conical orglobu- _ 
lar vessel, termed a receiver, connected with the retort. Where — 
the vapor is highly elastic or difficult of condensation, a series of re- 
ceivers connected together is necessary; and where it is incapable — 
of condensation by itself, but is easily absorbed by water, a jon 
of that fluid is disposed in the receiver, by which it is d.. 
Some bodies are impure on their first distillation ; they are purified 
by a second distillation, which is then termed rectification. Or, 
with the proper product of the distillation, a portion of aqueous vapor 
may have passed over: this may be abstracted by exposing the dis- 
tilled fluid again to heat, and the ss is named concentration or 
dephlegmation. 
SuBLimaTIon is another operation, by which a volatile matter is 
separated from one more fixed, by the application of heat; but the . 
matter volatilized is again condensed, not in the fluid but in the solid 
form. The operation, therefore, is generally performed in one ves- 
sel, the sublimate being condensed in the upper part. When it con- 
cretes in the form of light flakes, it was termed flowers, in the 
language of pharmacy. ata 
being excited and communicated in general by a furnace. 
Chemical combination is also frequently promoted by the appli- 
cation of-heat, even though the bodies are not fused. -Calcination is 
an operation of this kind. It is merely the exposing of a metal toa 
high temperature, with the free access of atmospheric air, by which 
itis oxygenated. Deflagration is an operation of a similar kind. 
It consists in mixing some salts, especially nitrate of potash, in which — 
pimae quantity of oxygen is retained with a very weak attractive 
ree, with any inflammable body, and exposing the mixture to heat. 
The oxygen is attracted by the inflammable substance, which is 
thusoxydated. 
Chemical decomposition is, in like manner, promoted by an in- 
crease of temperature. One principle of a compound, which 1s dis- 
- posed to volatility, may thus be expelled ; or two bodies, one or both 
of which are compounds, and which when mixed together have no 
action on each other, may, when exposed to a strong heat, exert at- 
fractions, by which their decomposition is effected. Pa 
are the principat operations of pharmacy. Connected vit 
of the subject, there remain to be noticed 
