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

184 THE METALLURGY OF ANTIMOKY.
bonate is added the metal is soon precipitated as antimonious hydrate,
upon which the iodine has no effect.
(/?) Volumetric Method of Petriccioli and Renter.—The antimonyore
is crushed, and 0*5 to 1 gramme of it is taken and treated first with
50 c.c. of hot water and then with 50 c.c. of pure strong hydrochloric
acid. It is heated on a sand-bath up to 70° C. All the antimony is
then dissolved in about from thirty to sixty minutes. It is next
filtered and the residue washed, first with water containing HOI and
then with pure water. The filtrate, after the addition of some tartaric
acid, is diluted to 750 c.c. and heated to 79° C. H2S is passed through
to obtain the precipitate. This is filtered, washed with H2S water,
and rinsed back into, the original precipitation vessel with the aid of
hot water. Add 50 c.c. of strong HC1 and warm the solution (but
avoid boiling) until no more H0S is evolved. Dilute the liquid
until a milkiness is just observed; this turbidity is removed by
adding HC1 drop by drop. Then titrate with potassium permanganate.
The reaction occurring is represented as follows :—
5SbCls+ 16HC1 + 2KMnO4 = 5SbCl82KCl + 2MnCl2 + 8KUO.
The end-point of the reaction is sharp. If 5*27 grammes of pure
potassium permanganate be dissolved per litre of solution, 1 c.c.
will be equivalent to 1 per cent, of antimony with 1 gramme
of the original sample.
(y) H. Causse,* in Comptes Rendus, 1897, describes a new method
for the volumetric estimation of antimony, which is based upon the
fact that antimonious acid, free or combined, reduces iodic acid, with
the formation of antimonic acid and the liberation of a proportionate
amount of iodine, the reaction being thus :—
5Sb2O3 + 4HIO3 = Sb2O5 + 41 + 2H2O.
The solutions required are: iodic acid, 50 grms. in 250 c.c. ; decinorrnal
sodium thiosulphate; 20 per cent, potassium iodide; and
starch paste. Into the flask of a Fresenius or Mohr's iodometric
apparatus, 0*5-0*6 gramme of antimonious oxide is weighed, 20-25
c.c. of iodic acid are added, and 10 c.c. of potassium iodide solution
are placed in the condensing apparatus. The contents of the flask are
boiled until colourless, and the collected iodine determined with
thiosulphate. From antimony compoxmds the sulphide is precipitated
by sulphuretted hydrogen, then dissolved in HC1, and the oxide
obtained by ffie action of sodium carbonate. The halogen acids,
sulphurous acid, and sulphuretted hydrogen must be dissolved in
* Taken from Mineral Industry.