be used when there is danger of a metallic oxide being
reduced, as in this case the metal would alloy with the platinum and
spoil the forceps. In this case charcoal should be used for the
support. If, however, there be oxides present which are not reduced by
the borax, then the platinum loop may be used. Tin is frequently used
for the purpose of enabling the bead to acquire a color for an oxide
in the reducing flame, by its affinity for oxygen. The oxide, thus
being reduced to a lower degree of oxidation, imparts its peculiar
tinge to the bead as it cools.

The arsenides and sulphides, before being examined, should be roasted,
and then heated with the borax bead. The arsenic of the former, it
should be observed, will act on the glass tube in which the
sublimation is proceeding, if the glass should contain lead.

It should be recollected that earths, metallic oxides, and metallic
acids are soluble in borax, except those of the easily reducible
metals, such as platinum or gold, or of mercury, which too readily
vaporize. Also the metallic sulphides, after the sulphur has been
driven off. Also the salts of metals, after their acids are driven off
by heat. Also the nitrates and carbonates, after their acids are
driven off during the fusion. Also the salts of the halogens, such as
the chlorides, iodides, bromides, etc., of the metals. Also the
silicates, but with great tardiness. Also the phosphates and borates
that fuse in the bead without suffering decomposition. The metallic
sulphides are insoluble in borax, and many of the metals in the pure
state.

There are many substances which give clear beads with borax both while
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 a