it soon tarnishes, being covered with a grey
matter, which some regard as a suboxide (Pb^{2}O), and others as
simply a mixture of lead and protoxide. At a glowing heat it is
oxidized to a protoxide, and at a white heat it is volatilized. It is
insoluble in most acids. It is, however, soluble in nitric acid, but
without decomposing water.

(_L._) _Protoxide of Lead_ (PbO).--It is an orange-colored powder,
which melts at a glowing temperature, and forms a lamellar mass after
cooling. Protoxide of lead absorbs oxygen from the atmosphere while
melting, which is given off again by cooling. Being exposed for a
longer while to the air, it absorbs carbonic acid and water, and
becomes white on the surface. It is soluble in nitric acid and caustic
alkalies. It forms with most acids insoluble salts. It is slightly
soluble in pure water, but not in water which contains alkaline salts.
This hydrate is white.

([beta].) _Red Oxide of Lead_ (PbO^{2}, PbO).--It forms a puce-colored
powder. It is insoluble in caustic alkalies. Hydrochloric acid
dissolves it and forms a yellow liquid, which is soon decomposed into
chloride of lead and chlorine. It is reduced by ignition to the
protoxide.

([gamma].) _Peroxide of Lead _(PbO^{2}).--It is a dark-brown powder.
It yields with hydrochloric acid the chloride of lead and chlorine
gas. When heated it liberates oxygen, and is reduced to the protoxide.

Lead combinations give the following reactions before the blowpipe:
Metallic lead tarnishes when heated in the oxidation flame, and is
instantly covered with a grey matter, consisting of the protoxide and
the metal. It fuses quickly, and is then covered with a
yellowish-brown protoxide until all the lead is converted into the
protoxide, which melts to a yellow liquid. In the reduction flame and
upon charcoal, it is volatilized, while the charcoal becomes covered
with a yellow sublimate of oxide. A little distance from the assay,
this sublimate appears white (carbonate of lead). Protoxide of lead
melts in the flame of oxidation to a beautiful dark yellow bead. In
the flame of reduction, and upon charcoal, it is reduced with
intumescence to metallic lead, which is volatilized by a continued
blast, and sublimates on charcoal, as mentioned above.

Red oxide of lead turns black when heated in the glass tube closed at
one end, and liberates oxygen, which is easily detected by the
introduction of an ignited splinter, when a more lively combustion of