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

12 THE METALLURGY OF ANTIMONY.
suddenly cooled. For its production a vacuum is used, such as that
employed for the production of yellow arsenic, heated inside by electricity
and cooled externally by liquid air. It can also be produced
by leading a current of oxygen into liquid antimony hydride at — 40°,
or by heating the yellow modification of antimony at - 90°.
This black modification is amorphous, has a specific gravity of 5*3,
and is easier liquefied and is more active chemically than the ordinary
metallic form. It oxidises easily in the air under ordinary temperature,
and is sometimes spontaneously combustible. At 100° it
changes gradually to the ordinary metal, but suddenly at 400°.
Yellow Antimony.—It is the most unstable of all the modifications
of antimony. It was discovered by Stock, Guttmann, and Siebert,
and corresponds to white phosphorus and yellow arsenic. It cannot
be produced by a sudden cooling of antimony vapour, but only by
introducing oxygen into antimony hydride at - 90°. The reaction
can be accelerated by ozonising. It can also be produced by the
action of chlorine upon antimony hydride.
As stated, it is very unstable and changes into the black modification
above - 90° under ordinary light.
Chemical Properties.—Pure antimony oxidises very little at the
ordinary temperature. By being heated it is converted into the
trioxide, which rises in the form of smoke from the upper surface of
the metal. It can also be oxidised by any oxides that can easily give
up their oxygen component, e.g. manganese peroxide, quicksilver,
lead oxides, etc. It can also be oxidised in the presence of steam.
Hydrogen reduces the trioxide.
In concentrated nitric acid the metal can be converted into the
trioxide or the pent oxide through the agency of nitrous oxide.
Which oxide is produced depends entirely upon the' temperature and
the concentration. Powdered antimony, particularly if previously
heated, is powerfully acted upon by chlorine and bromine, resulting
in the production of pentachlorides or pentabromidos, with evolution
of light.
Antimony is attacked by hydrochloric acid only when it is in the
state of very fine powder. Dilate sulphuric acid does not attack it,
while with hot concentrated acid it forms antimonious sulphate.
Aqua regia in the cold dissolves it easily, forming the pentachloride.
When ignited with a mixture of nitre and soda it explodes, forming
an alkaline antimoniate. With alkaline nitrate and chlorate the
metal decrepitates, resulting in the formation of an antimoniato.
The metalloids, with the exception of boron, carbon, and silicon
form compounds with antimony.