ACETOUS ACID.
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mon uſes, it is only purified by distillation, and it is then known by
the name of Distilled Vinegar. It resembles the fossil acids by effre
vescing with alkalis in their ordinary state, and by uniting with them,
and with absorbent earths, and some metals, though weakly. Like
thofe acids, it changes vegetable colours to red, but it has little effect
upon inflammable bodies, though it may be combined with them, nôr
is it so acrid and corrosive, even when equal in strength.
But there is another remarkable particular by which it differs from
the fossil acids, viz. by being easily destructible by the action of
heat, if the heat to which it is exposed ever rises to the point of igni
tion. We may observe the effects of this heat upon it, by joining to
it some fixed substance that can retain it, and repress its volatility with
proper force, such as a fixed alkali. If it be united to one of these, and
the compound exposed to heat in close vessels, as soon as the com
pound salt approaches to a red heat, the acid begins to be totally de
stroyed. The principles of it are disarranged, and made to enter in
to new combinations with one another, so that we never can recover
it again. It is scorched, burned, and destroyed by the heat, and con
verted into foetid, watery, and oily steams, and a black coaly matter
adheres to the alkali.
The fame change is produced by fire on all vegetable matter in ge
neral; and as all other vegetable matter is inflammable, so is also this
acid.
SPECIES V.—ACID OF TARTAR.
The other species of vegetable acid, which is known by the name
of the acid of tartar, or the tartarous acid, is still more gross, and far
ther removed from the nature of the more pure and perfect salts. For
although we can reduce it to a dry state, and crystallize it, it is nei
ther a fusible nor a volatile substance. I mean that, except a watery