any department of science.

Nitric Acid--Exists in combination with the bases, potash, soda, lime,
magnesia, in both the mineral and vegetable kingdoms, and is never
found insoluble. It has the same constituents as common air, but in
different proportions. The strongest nitric acid contains in every
pound, two and a quarter ounces of water. Pure nitric acid is
colorless, with a specific gravity of 1.5, and boiling at 248 deg.. It
is a most powerful oxidizing agent, and is decomposed with more or less
rapidity, by almost all the metals, to which it yields a portion of its
oxygen.

The nitric acid of commerce, is generally the article used by the
Daguerreotypist. This usually contains some chlorine and sulphuric
acid. It is obtained by the distillation of saltpetre with sulphuric
acid. It is employed in the Daguerreotype process for dissolving
silver, preparing chloride or oxide, nitrate of silver, [the former
used in galvanizing,] and in combination with muriatic acid for
preparing chloride of gold, used in gilding. It is also used by some
for preparing the plate.

Acidulated Solution.--This solution is used for cleaning the surface of
the Daguerreotype plate. It has the property of softening the silver,
and bringing it to a state in which it is very susceptible of being
either oxidized or iodized, hence it contributes to increase the
sensibility of the plate. The proportions are to one drop of acid add
from 15 to 20 drops of water, or make the solution about like sharp
vinegar to the taste.

Nitro-Muriatic Acid.--Aqua Regia is a compound menstruum invented by
the alchemists for dissolving gold. It is composed of colorless nitric
acid (aqua-fortis) and ordinary muriatic acid; the mixture is yellow,
and acquires the power of dissolving gold and platinum. These
materials are not properly oxidized; it nearly causes their combination
with chlorine, which is in the Muriatic acid.

Hydrochloric Acid (Muriatic Acid).--This acid forms a valuable addition
to the chemicals employed by the practical Daguerreotypist. This acid
is formed by acting upon common salt (which is chloride of sodium) by
concentrated sulphuric acid. The water of the acid is decomposed, and
its hydrogen combines with the chloride of the salt to form muriatic
acid, and this unites with the sulphuric acid to form sulphate of soda;
60 parts of common salt and 49 parts of concentrated sulphuric acid,
afford, by this mutual action, 37 parts of