olatilized, and the
bead appears clear again, while a white sublimate is deposited upon
the charcoal.

With microcosmic salt, the same reactions are produced.

With carbonate of soda, tellurous acid fuses upon platinum wire to a
clear colorless bead, which is white when cold. Upon charcoal it is
reduced, and forms _tellur-sodium_, which is absorbed by the charcoal,
and metallic tellurium, which is volatilized, and deposits upon the
charcoal a white incrustation (tellurous acid).

If tellurous acid, finely powdered charcoal, and carbonate of soda are
mixed together, and the mixture be well ignited in a closed tube,
until fusion is effected, and a few drops of boiled water are brought
into the tube, they are colored purple, indicating the presence of
_tellur-sodium._

_Telluric Acid _(TeO^{3}) forms six-sided prismatic crystals. It has
not an acid, but rather a metallic taste. It changes blue litmus paper
to red; is slowly soluble in water, and rather sparingly. Exposed to
a high temperature, but not until glowing, the crystalline acid loses
its water, and acquires an orange color, but still it preserves its
crystalline form, although no longer soluble in water, and is in fact
so much changed in its properties as to present the instance of an
isomeric modification.

If telluric acid is heated gently in a closed tube, it loses water and
turns yellow. Heated still more strongly, it becomes milk-white,
oxygen is expelled, and it is converted into tellurous acid. The
presence of oxygen can be recognized by the more lively combustion
which an ignited splinter of wood undergoes when held in it. Telluric
acid produces the same reactions with the blowpipe reagents as
tellurous acid.

SEVENTH GROUP.--LEAD, BISMUTH, TIN.

The oxides of these metals are also reduced to the metallic state by
fusion with soda upon charcoal in the flame of reduction, but they are
volatilized only after a continued blast, and a sublimate is thrown
upon the charcoal.

(_a._) _Lead_ (Pb).--This metal occurs in considerable quantity in
nature, chiefly as galena or lead-glance (sulphide of lead). Likewise,
but more rarely, as a carbonate; also as a sulphate, and sometimes
combined with other acids and metals.

In the metallic state, lead is of a bluish-grey color, high lustre,
and sp. gr. 11.4. It is soft, and communicates a stain to paper. It is
malleable, ductile, but has very little tenacity. It melts at about
612 deg.. Exposed to the air