considerable quantity of oxide an amethyst color is
obtained, but never so dark as in borax. With but little oxide a
colorless bead is obtained, in which, however, the
amethyst-color may be brought out by adding a little nitre.
While the bead is kept fused, it froths and gives off bubbles of
gas.

in the reducing flame.

The colored bead immediately loses its color, either on platinum
wire or on charcoal. After the reduction the fluid bead remains
still.

* * * * *

5. Oxide of Iron, Fe^{2}O^{3}.

Behavior with Borax on Platinum wire

in the oxidizing flame.

With a small proportion of oxide, the glass is of a yellow
color, while warm, and colorless when cold; with a larger
proportion, red, while warm, and yellow, when cold; and with a
still larger amount, dark-red, while warm, and dark-yellow, when
cold.

in the reducing flame.

Treated alone on platinum wire, the glass becomes of a
bottle-green color (F^{3}O^{4}), and if touched with tin, it
becomes of a pale sea-green. On charcoal with tin, it assumes at
first a bottle-green color, which by continued blowing changes
to a sea-green (FeO).

Behavior with Mic. Salt on Platinum wire

in the oxidizing flame.

With a certain amount of oxide, the glass is of a yellowish-red
color, which on cooling changes to yellow, then green, and
finally becomes colorless. With a large addition of oxide, the
color is, when warm, dark red, and passes, while cooling, into
brownish-red, dark green, and finally brownish-red. During the
cooling process, the colors change more rapidly than with borax.

in the reducing flame.

With a small proportion of oxide there is no reaction. With a
larger amount the bead is red, while warm, and becomes on
cooling successively yellow, green, and russet. With the
addition of tin the glass becomes, during cooling, first green
and then colorless.

* * * * *

6. Oxide of Cobalt, CoO.

Behavior with Borax on Platinum wire

in the oxidizing flame:

Colors the glass of an intense smalt blue both whilst hot and
when cold. When much oxide is present, the color is so deep as
to appear black.

in the reducing flame:

As in the oxidizing flame.