ccess of air,
metallic tellurium sublimes with the deposition of a grey powder.
Bismuth produces, under similar treatment, scarcely any vapor, unless
it is combined with sulphur. The metal is enveloped by fused oxide of
a dark yellow color, which appears light yellow after being cooled. It
acts upon the glass, and dissolves it.

3. Upon charcoal, exposed to the blowpipe flame, the three metals are
volatilized, and yield a sublimate upon the charcoal. That of antimony
is white, while those of bismuth and tellurium are dark yellow. By
exposing them to the flame of reduction, the sublimate of tellurium
disappears and communicates an intense green color to the flame. The
antimony incrustation gives a feeble greenish-blue color, while the
sublimate of bismuth gives no perceptible color in the light. It is,
however, worthy of notice that if the operation takes place in the
dark, a very pale blue flame will be seen with the bismuth.

(_c._) _Tin_ (Sn).--This metal does not occur in nature in the
metallic state, very seldom in the sulphide, but chiefly in the oxide
(tinstone). In the metallic state it is silver-white, possesses a very
high lustre, is soft (but harder than lead), ductile, but has not much
tenacity, and it is very malleable. The metal when it is cast gives a
peculiar creaking noise when twisted or bent, which proceeds from the
crystalline structure of the metal. This crystallization is quite
clearly manifested by attacking the surface of the metal, or that of
tin plate, with acids.

Tin is very slightly tarnished by exposure to the air. It fuses at
442 deg., and becomes grey, being a mixture of the oxide and the metal. At
a high temperature even, tin is but little subject to pass off as
vapor. It is soluble in aqua regia, and with the liberation of
hydrogen, in hot sulphuric and hydrochloric acids, and in cold dilute
nitric acid, without decomposing water, or the production of a gas,
while nitrate of tin and nitrate of ammonia are formed. Concentrated
nitric acid converts tin into insoluble tin acids.

([alpha].) _Protoxide of Tin_ (SnO) is a dark-grey powder. Its hydrate
is white, and is soluble in caustic alkalies. When this solution is
heated, anhydrous crystalline black protoxide is separated. The
soluble neutral salts of tin-protoxide are decomposed by the addition
of water, and converted into acid soluble, and basic insoluble salts.

When protoxide of tin is ignited with free access of air, it takes
f