Dissolves to a clear yellow glass, which assumes a
yellowish-green color on cooling.

in the reducing flame.

The glass assumes a beautiful green color, which becomes more
brilliant as the bead cools. The addition of tin upon charcoal
produces no further change.

* * * * *

14. Oxide of Copper, CuO.

Behavior with Borax on Platinum wire

in the oxidizing flame.

Produces an intense coloration. If in small quantity, the glass
is green, while warm, and becomes blue on cooling. If in large
proportion, the green color is so intense as to appear black.
When cool, this becomes paler, and changes to a greenish blue.

in the reducing flame.

If not too saturated, the cupriferous glass soon becomes nearly
colorless, but immediately on solidifying assumes a red color
and becomes opaque. By long continued blowing on charcoal, the
copper in the bead is reduced and separates out as a small
metallic bead, leaving the glass colorless. With the addition of
tin, the glass becomes of an opaque dull-red on cooling.