and which then powerfully reddens litmus paper, is decanted.
It is also a little colored, but remains very limpid.

Solution of Chloride of Gold and Platinum.--In order not to
multiply the solutions, take the ordinary chloride of gold,
used for fixing the impressions, and which is composed of 1
gramme of chloride of gold and 50 grains of hyposulphate of soda,
to a quart of distilled water.

With respect to chloride of platinum, 4 grains must be dissolved in 3 quarts
of distilled water; these two solutions are mixed in equal quantities.

Acids.--I shall not go into the preparations of the various acids
employed in the Daguerreotype. This would be useless to the operator,
as there are few, if any, that it would be advisable to prepare.
It is only necessary for the experimenter to be made acquainted with
their properties, and this in order to prevent any haphazard experiments,
which are too common among operators. Any person who may be desirous
to try an experiment, should first study the agents he wishes to employ.
By so doing much time and money will be saved; while the searcher after
new discoveries would rarely become vexed on account of his own ignorance,
or be obliged to avail himself of the experience of others in 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,