l white crystals. If this
white sublimate upon the charcoal is moistened with a solution of
cobalt-oxide, and exposed to the reduction flame, a part of it is
volatilized, while the other part passes into higher oxidation, and
remains, after cooling, of a dirty dark-green color.

(_d._) _Tellurium_ (Te).--This is one of the rare metals. It occurs
very seldom in the metallic state, but often with bismuth, lead,
silver, and gold. Tellurium, in the pure state, is silver-white, very
bright, of a foliated or lamellar structure, brittle, and easily
triturated. It is inclined to crystallize. It is soluble in
concentrated sulphuric acid without oxidation. The solution is of a
fine purple color, and gives a precipitate with the addition of water.

_Tellurium in the Metallic form._--By the aid of heat it is oxidized
in sulphuric acid, a portion of the oxygen of the acid oxidizing the
metal, while sulphurous acid gas escapes. This solution is colorless,
and is tellurous acid, dissolved in sulphuric acid. It melts at a low
red heat, and volatilizes at a higher temperature. If tellurium is
heated with free access of air, it takes fire, and burns with a blue
color, the flame being greenish at the edges, while a thick white
vapor escapes, which has a feeble acidulous odor.

_Tellurous Acid_ (TeO^{2}) is of a fine, granulous, crystalline or
white earthy mass, which is partly soluble in water. The solution has
a strong metallic taste, and an acid reaction upon litmus paper.
Heated in a tube closed at one end until it begins to glow, it fuses
to a yellow liquid which is colorless, crystalline, and opaque when
cold. Beads of it remain usually transparent like glass. Heated upon
platinum wire in the flame of oxidation, it melts, and is volatilized
as a white vapor. When heated upon charcoal in the oxidation flame, it
melts, and is reduced to the metallic state, but volatilizes and a
sublimate of white tellurous acid is formed upon the charcoal. The
edge of this deposit is usually red or dark-yellow.

Heated upon charcoal in the flame of reduction, it is rapidly reduced,
the external flame exhibiting a bluish-green color.

Borax dissolves it in the oxidation flame upon platinum wire to a
clear colorless bead which turns grey when heated upon charcoal,
through the presence of reduced metallic particles. Upon charcoal, in
the reduction flame, the bead is grey, caused by the reduced metal.
After a continued blast, tellurium is completely v