in the cucurbit; with this view, the sides of the capital must always be
preserved at a lower temperature than is necessary for keeping the
distilling substance in the state of gas, and the water in the
refrigetory is intended for this purpose. Water is converted into gas
by the temperature of 80 (212 ), alkohol by 67 (182.75 ), ether by 32
(104 ); hence these substances cannot be distilled, or, rather, they
will fly off in the state of gas, unless the temperature of the
refrigetory be kept under these respective degrees.
In the distillation of spiritous, and other expansive liquors, the above
described refrigetory is not sufficient for condensing all the vapours
which arise; in this case, therefore, instead of receiving the distilled
liquor immediately from the beak, TU, of the capital into a recipient, a
worm is interposed between them. This instrument is represented Pl. III.
Fig. 18. contained in a worm tub of tinned copper, it consists of a
metallic tube bent into a considerable number of spiral revolutions. The
vessel which contains the worm is kept full of cold water, which is
renewed as it grows warm. This contrivance 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
255