zinc zinc.
manganese manganese.
iron iron.
lead lead.
tin tin.
cobalt cobalt.
copper copper.
nickel nickel.
bismuth bismuth.
mercury mercury.
antimony antimony.
silver silver.
gold gold.
platina platina.
Argill argill.
_Note._--This order of salts was entirely unknown to the antient
chemists. Mr Macquer, in 1746, discovered the combinations of arseniac
acid with potash and soda, to which he gave the name of _arsenical
neutral salts_.--A.
SECT. XXIII.--_Observations upon Arseniac Acid, and its Combinations._
In the Collections of the Academy for 1746, Mr Macquer shows that, when
a mixture of white oxyd of arsenic and nitre are subjected to the action
of a strong fire, a neutral salt is obtained, which he calls _neutral
salt of arsenic_. At that time, the cause of this singular phenomenon,
in which a metal acts the part of an acid, was quite unknown; but more
modern experiments teach that, during this process, the arsenic becomes
oxygenated, by carrying off the oxygen of the nitric acid; it is thus
converted into a real acid, and combines with the potash. There are
other methods now known for oxygenating arsenic, and obtaining its acid
free from combination. The most simple and most effectual of these is as
follows: Dissolve white oxyd of arsenic in three parts, by weight, of
muriatic acid; to this solution, in a boiling state, add two parts of
nitric acid, and evaporate to dryness. In this process the nitric acid
is decomposed, its oxygen unites with the oxyd of arsenic, and converts
it into an acid, and the nitrous radical flies off in the state of
nitrous gas; whilst the muriatic acid is converted by the heat into
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