with this salt, the microscosmic salt is
used the same as borax.

9. _Nitrate of Cobalt._--(CoO, NO^{5}).--This salt can be prepared by
dissolving pure oxide of cobalt in diluted nitric acid, and
evaporating to dryness with a low heat. The dry residue should be
dissolved in ten parts of water, and filtered. The filtrate is now
ready for use, and should be kept in a bottle with a glass stopper. If
the pure oxide of cobalt cannot be procured, then it may be prepared
by mixing two parts of finely powdered _glance of cobalt_ with four
parts of saltpetre, and one part of dry carbonate of potassa with one
part of water free from carbonate of soda. This mixture should be
added in successive portions into a red-hot Hessian crucible, and the
heat continued until the mass is fused, or at least greatly diminished
in volume. The cooled mass must be triturated with hot water, and then
heated with hydrochloric acid until it is dissolved and forms a dark
green solution, which generally presents a gelatinous appearance,
occasioned by separated silica. The solution is to be evaporated to
dryness, the dry residue moistened with hydrochloric acid, boiled with
water, filtered and neutralized while hot with carbonate of ammonia,
until it ceases to give an acid reaction with test-paper. This must
now be filtered again, and carbonate of potassa added to the filtrate
as long as a precipitate is produced. This precipitate is brought upon
a filter and washed thoroughly, and then dissolved in diluted nitric
acid. This is evaporated to dryness, and one part of it is dissolved
in ten parts of water for use.

The oxide of cobalt combines, with strong heat in the oxidation flame,
with various earths and infusible metallic oxides, and thus produces
peculiarly colored compounds, and is therefore used for their
detection; (alumina, magnesia, oxide of zinc, oxide of tin, etc.) Some
of the powdered substance is heated upon charcoal in the flame of
oxidation, and moistened with a drop of the solution of the nitrate of
cobalt, when the oxidation flame is thrown upon it. Alumina gives a
pure blue color, the oxide of zinc a bright green, magnesia a light
red, and the oxide of tin a bluish-green color; but the latter is only
distinctly visible after cooling.

The dropping bottle, is the most useful apparatus for the purpose of
getting small quantities of fluid. It is composed of a glass tube,
drawn out to a point, with a small orifice. This tube passes th