,
and weighed. The precipitate is thallous iodide TlI, and contains 61.6
per cent. of thallium.
BISMUTH.
Bismuth is nearly always found in nature in the metallic state; but
occasionally it is met with as sulphide in bismuthine and as carbonate
in bismutite. It is also found in some comparatively rare minerals, such
as tetradymite, combined with tellurium, and associated with gold. In
minute quantities it is widely distributed: it is a common constituent
of most copper ores; hence it finds its way into refined copper, which
is seldom free from it. It is occasionally met with in silver in
sufficient quantity to interfere with the working qualities of that
metal.
Bismuth compounds are used in medicine and in the manufacture of alloys.
Bismuth possesses many useful properties. It has considerable commercial
value, and sells at a high price.
The metal is brittle, breaks with a highly crystalline fracture, and has
a characteristic reddish-yellow colour. It is almost insoluble in
hydrochloric, but readily dissolves in nitric, acid; and gives, if the
acid is in excess, a clear solution. Bismuth salts have a strong
tendency to separate out as insoluble basic compounds; this is more
especially true of the chloride which, on diluting with a large volume
of water, becomes milky; the whole of the bismuth separating out.
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