A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...

THE CHEMISTRY OF ANTIMONY. 13
SECTION 3.—THE COMPOUNDS OF ANTIMONY.
Antimony has three valences, 3, 4, and 5.* Its chemical properties
are very similar to those of arsenic. In other ways it stands
close to the zinc group, particularly to the elements germanium and
zinc. The likeness between antimony and germanium is so close that
the discoverer of the latter at first called it Eka-antimony of
Olendelejeff. Analytically, antimony presents some difficulty in its
separation from zinc.
A. The Compounds of Antimony of 3 Valences.
In this condition antimony is a weak base and possesses an electropositive
character. Its ion concentration is not great.
Antimony Hydride, SbH3.—It corresponds to phosphorus hydride
(PH3) and arsenic hydride (AsH3). It was discovered by Lewis
Thompson in 1837, and about the same time independently by Pfaff.
However, the production of pure antimony hydride and the determination
of its physical constants are matters of recent times.
It is formed when hydrogen is generated in the presence of a
soluble antimony compound, or when the compounds of antimony
and the alkali metals are decomposed by water, or when an antimonyzinc
alloy is treated with sulphuric acid or hydrochloric acid.
It can also be formed when metallic zinc is treated with a weak
solution of hydrochloric acid or of sulphuric acid on the addition of
a solution of antimony salt.
According to Stock and Doht, 1 gram of the alloy of zinc and
antimony (Zn:Sb = 4:l) in a mixed solution of tartaric acid and
hydrochloric acid can produce 0*1 to 0*15 gram of pure antimony
hydride. But according to Stock and Guttmann a better result
could be obtained by putting finely powdered magnesium antirnonide
(Sb : Mg = 1:2) into a cold weak solution of hydrochloric acid.
Antimony hydride is a colourless, inflammable gas with a characteristic
damp and weak hydrogen sulphide smell. It burns with a
greenish flame, producing a white smoke of steam and antimony
trioxide. 1 cm. 3 weighs 5 - 302 mgrms. at 0° and 754 mm. pressure.
On an average it is 4360 times heavier than air and 3994 times
heavier than oxygen. The observed density, on account of molecular
association or of molecular attraction, is 2*95 per cent, more
than the theoretical one.
The boiling-point of the liquid is -18° (Olszewski). The specific
* May bo called tri-, quadri-, quinqui-.