is
combination, instead of being essential to their constitution, can only
be considered as a foreign substance, which contaminates their purity.
It is the province of the advocates[23] for this system to prove, by
decisive experiments, the real existence of this combined hydrogen,
which they have hitherto only done by conjectures founded upon
suppositions.

FOOTNOTES:

[22] This term _alloy_, which we have from the language of the arts,
serves exceedingly well for distinguishing all the combinations or
intimate unions of metals with each other, and is adopted in our new
nomenclature for that purpose.--A.

[23] By these are meant the supporters of the phlogistic theory, who at
present consider hydrogen, or the base of inflammable air, as the
phlogiston of the celebrated Stahl.--E.

CHAP. XI.

_Observations upon Oxyds and Acids with several Bases--and upon the
Composition of Animal and Vegetable Substances._

We have, in Chap. V. and VIII. examined the products resulting from the
combustion of the four simple combustible substances, sulphur,
phosphorus, charcoal, and hydrogen: We have shown, in Chap. X that the
simple combustible substances are capable of combining with each other
into compound combustible substances, and have observed that oils in
general, and particularly the fixed vegetable oils, belong to this
class, being composed of hydrogen and charcoal. It remains, in this
chapter, to treat of the oxygenation of these compound combustible
substances, and to show that there exist acids and oxyds having double
and triple bases. Nature furnishes us with numerous examples of this
kind of combinations, by means of which, chiefly, she is enabled to
produce a vast variety of compounds from a very limited number of
elements, or simple substances.

It was long ago well known, that, when muriatic and nitric acids were
mixed together, a compound acid was formed, having properties quite
distinct from those of either of the acids taken separately. This acid
was called _aqua regia_, from its most celebrated property of dissolving
gold, called _king of metals_ by the alchymists. Mr Berthollet has
distinctly proved that the peculiar properties of this acid arise from
the combined action of its two acidifiable bases; and for this reason we
have judged it necessary to distinguish it by an appropriate name: That
of _nitro-muriatic_ acid appears extremely applicable, from its
expressing the nature of the two substa