antimony - Sciencemadness.org

20 THE METALLURGY OF ANTIMONY.
Sb04. Sulphur reacts upon the trioxide with the formation of antimony
sulphide and sulphur dioxide. With antimony sulphide the
trioxide melts without decomposition, forming the so-called antimonyglass.
The trioxide, especially in the form of vapour, is poisonous.
The equilibrium existing between the trioxide, the tetroxide, and
oxygen, and also the partial pressure exercised by the oxygen, when
the metal is heated in the air, are still unknown.
Antimony Hydroxides or Hydrates.—The three possible hydrates
of antimony, as derived from antimony trioxide, are:—
HSb03=(Sb203 + H20) or(SbO)OH, metantimonious acid or monohydrate
or metahydrate.
H4Sb2O5 = (Sbo03 + 2H2O), pyro-antiraonious acid.
Sb{OH)3 = (Sb2O3 + 3H2O), ortho-anthnonious acid.
HSbO2 is obtained by decomposing tartrate of antimony and
potassium with acetate or alkaline carbonate (Long), This hydrate
presents the character rather of a base than of an acid. Nevertheless
it can give rise to the formation of antimonites.
H4Sb.,O5 is obtained by dissolving antimony trisulphide in an alk aline
liquor, which is subsequently sulphurised by the addition of copper
sulphate (Fresenius and Schaffner) until a portion of the liquid,
filtered off, gives, with an acid, a white precipitate. Aided by heat,
it changes gradually to the anhydride form, even in the presence
of water. The dissociation tension (Dissoziationsspannung) of this
hydrate is greater than the vapour-pressure of water. Serono doubts
the existence of this hydrate.
SbO3Hs (Clarice and Stallo) is obtained by decomposing tartrate of
antimony and barium with an equivalent quantity of cold dilute
sulphuric acid. After nitration, the liquid gradually gives rise to a
deposit of white powder, which is then carefully washed and dried
at 110°.
These hydrates are not known as crystals. They are amphoteric
in character; on the one hand they behave like acids, forming antimonites
with the alkalies, and on the other hand like bases, forming
salts of the acids used.
AntiTnonites.—They are salts formed from the acids derived from
Sb.-jOg, and are obtained from a solution of antimony hydroxides in
alkaline liquor. The sodium salts derived from HSbO2 are:—
Sp. Gr.
NaSbOo-SBy) Octahedron. 2*86 Very hard to dissolve in hot water.
2saSbO2.2HSbO2 Large crystals. 5*05 Almost insoluble in water.
A solution of sodium metantimonite gives a precipitate from
the salts of heavy metals. Cupric antimonite is precipitated when