he bead, if pretty well saturated, becomes dark-green
while hot, and brownish-red when cool, opaque and enamel-like. If the
oxide is so little that no reaction is visible, by the addition of
some tin, the bead appears colorless while hot, and dark brownish-red
and opaque when cold.

_Carbonate of Soda_ dissolves oxide of copper in the oxidation flame
upon platinum wire, to a clear, green bead, which loses its color when
cooling, and becomes opaque.

Upon charcoal, it is reduced to the metal, the soda is absorbed by the
charcoal, and the metallic particles melt with sufficient heat to a
grain.

(_b._) _Silver_ (Ag).--This metal occurs in nature in the metallic
state, and in combination with other metals, particularly with lead.
It also occurs as the sulphide in several mines. It crystallizes in
cubes and octahedrons; is of a pure white color, great lustre, is very
malleable and ductile, and is softer than copper, but harder than
gold. It is not oxidizable, neither at common temperatures nor at
those which are considerably higher. It is soluble in dilute nitric
acid, and in boiling concentrated sulphuric acid.

([chi].) _Protoxide of Silver_ (Ag^{2}O).--It is a black powder. It is
converted by acids and ammonia into oxide and metal.

([beta].) _Oxide of Silver_ (AgO).--It is a greyish-brown or black
powder, and is the base of the silver salts. With aqua ammonia, it is
converted into the black, fulminating silver.

([gamma].) _Superoxide or Binoxide of Silver_ (AgO^{2}).--This oxide
occurs in black needles or octahedral crystals of great metallic
lustre. It is dissolved by the oxygen acids with the disengagement of
oxygen gas.

_Behavior before the Blowpipe._--When exposed to the flames of
oxidation and reduction, the oxides of silver are instantly reduced to
the metallic state.

_Borax_ dissolves silver-oxides upon platinum wire in the oxidation
flame but partially, while the other portion is reduced, the bead
appearing opalescent after cooling, in correspondence to the degree of
saturation. The bead becomes grey in the flame of reduction, the
reduced silver melting to a grain, and the bead is rendered clear and
colorless again.

_Microcosmic Salt_ dissolves oxides of silver in the flame of
oxidation upon platinum wire to a transparent yellowish bead, which
presents, when much of the oxide is present, an opalescent appearance.

In the flame of reduction, the reaction is analogous to that of borax.

By fusio