nce is employed in all
distilleries of spirits, without the intervention of a capital and
refrigetory, properly so called. The one represented in the plate is
furnished with two worms, one of them being particularly appropriated to
distillations of odoriferous substances.

In some simple distillations it is necessary to interpose an adopter
between the retort and receiver, as shown Pl. III. Fig, 11. This may
serve two different purposes, either to separate two products of
different degrees of volatility, or to remove the receiver to a greater
distance from the furnace, that it may be less heated. But these, and
several other more complicated instruments of ancient contrivance, are
far from producing the accuracy requisite in modern chemistry, as will
be readily perceived when I come to treat of compound distillation.

SECT. VI.

_Of Sublimation._

This term is applied to the distillation of substances which condense in
a concrete or solid form, such as the sublimation of sulphur, and of
muriat of ammoniac, or sal ammoniac. These operations may be
conveniently performed in the ordinary distilling vessels already
described, though, in the sublimation of sulphur, a species of vessels,
named Alludels, have been usually employed. These are vessels of stone
or porcelain ware, which adjust to each other over a cucurbit containing
the sulphur to be sublimed. One of the best subliming vessels, for
substances which are not very volatile, is a flask, or phial of glass,
sunk about two thirds into a sand bath; but in this way we are apt to
lose a part of the products. When these are wished to be entirely
preserved, we must have recourse to the pneumato-chemical distilling
apparatus, to be described in the following chapter.

CHAP. VI.

_Of Pneumato-chemical Distillations, Metallic Dissolutions, and some
other operations which require very complicated instruments._

SECT. I.

_Of Compound and Pneumato-chemical Distillations._

In the preceding chapter, I have only treated of distillation as a
simple operation, by which two substances, differing in degrees of
volatility, may be separated from each other; but distillation often
actually decomposes the substances submitted to its action, and becomes
one of the most complicated operations in chemistry. In every
distillation, the substance distilled must be brought to the state of
gas, in the cucurbit or retort, by combination with caloric: In simple
distillation, th