hot and cold, but which, upon being heated with the intermittent
oxidation flame, become enamelled and opaque. The intermittent flame
may be readily attained, not by varying the force of the air from the
mouth, but by raising and depressing the bead before the point of the
steady oxidating flame. The addition of a little nitrate of potash
will often greatly facilitate the production of a color, as it
oxidizes the metal. The hot bead should be pressed upon a small
crystal of the nitrate, when the bead swells, intumesces, and the
color is manifested in the surface of the bead,


6. EXAMINATIONS IN MICROCOSMIC SALT.


Microcosmic salt is a better flux for many metallic oxides than borax,
as the colors are exhibited in it with more strength and character.
Microcosmic salt is the phosphate of soda and ammonia. When it is
ignited it passes into the biphosphate of soda, the ammonia being
driven off. This biphosphate of soda possesses an excess of phosphoric
acid, and thus has the property of dissolving a great number of
substances, in fact almost any one, with the exception of silica. If
the substances treated with this salt consist of sulphides or
arsenides, the bead must be heated on charcoal. But if the substance
experimented upon consists of earthly ingredients or metallic oxides,
the platinum wire is the best. If the latter is used a few additional
turns should be given to the wire in consequence of the greater
fluidity of the bead over that of borax. The microcosmic salt bead
possesses the advantage over that of borax, that the colors of many
substances are better discerned in it, and that it separates the
acids, the more volatile ones being dissipated, while the fixed ones