mercury mercury.
molybdena molybdena.
nickel nickel.
gold gold.
platina platina.
lead lead.
Potash potash.
Soda soda.
Oxyd of
tungstein tungstein.
zinc zinc.

_Note._--Most of these combinations, especially those with the earths
and alkalies, have been little examined, and we are yet to learn whether
they form a mixed salt in which the compound radical remains combined,
or if the two acids separate, to form two distinct neutral salts.--A.

SECT. XX.--_Observations upon the Nitro-Muriatic Acid, and its
Combinations._

The nitro-muriatic acid, formerly called _aqua regia_, is formed by a
mixture of nitric and muriatic acids; the radicals of these two acids
combine together, and form a compound base, from which an acid is
produced, having properties peculiar to itself, and distinct from those
of all other acids, especially the property of dissolving gold and
platina.

In dissolutions of metals in this acid, as in all other acids, the
metals are first oxydated by attracting a part of the oxygen from the
compound radical. This occasions a disengagement of a particular species
of gas not hitherto described, which may be called _nitro-muriatic gas_;
it has a very disagreeable smell, and is fatal to animal life when
respired; it attacks iron, and causes it to rust; it is absorbed in
considerable quantity by water, which thereby acquires some slight
characters of acidity. I had occasion to make these remarks during a
course of experiments upon platina, in which I dissolved a considerable
quantity of that metal in nitro-muriatic acid.

I at first suspected that, in the mixture of nitric and muriatic acids,
the latter attracted a part of the oxygen from the former, and became
converted into oxygenated muriatic acid, which gave it the property of
dissolving gold; but several facts remain inexplicable upon this
supposition. Were it so, we must be able to disengage nitrous gas by
heating this acid, which however does not sensibly happen. From these
considerations, I am led to adopt the opinion of Mr Berthollet, and to
consider nitro-muriatic acid as a single acid, with a compound base or
radical.

TABLE _of the Combinations of Fluoric Acid, with the Salifiable Bases,
in the Order of Affinity._

_Names of the Bases._ _N