A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...
A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...
A N T I M O N Y : ITS HISTORY, CHEMISTRY, MINERALOGY ...
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184 THE METALLURGY OF ANTIMOKY.<br />
bonate is added the metal is soon precipitated as antimonious hydrate,<br />
upon which the iodine has no effect.<br />
(/?) Volumetric Method of Petriccioli and Renter.—The antimonyore<br />
is crushed, and 0*5 to 1 gramme of it is taken and treated first with<br />
50 c.c. of hot water and then with 50 c.c. of pure strong hydrochloric<br />
acid. It is heated on a sand-bath up to 70° C. All the antimony is<br />
then dissolved in about from thirty to sixty minutes. It is next<br />
filtered and the residue washed, first with water containing HOI and<br />
then with pure water. The filtrate, after the addition of some tartaric<br />
acid, is diluted to 750 c.c. and heated to 79° C. H2S is passed through<br />
to obtain the precipitate. This is filtered, washed with H2S water,<br />
and rinsed back into, the original precipitation vessel with the aid of<br />
hot water. Add 50 c.c. of strong HC1 and warm the solution (but<br />
avoid boiling) until no more H0S is evolved. Dilute the liquid<br />
until a milkiness is just observed; this turbidity is removed by<br />
adding HC1 drop by drop. Then titrate with potassium permanganate.<br />
The reaction occurring is represented as follows :—<br />
5SbCls+ 16HC1 + 2KMnO4 = 5SbCl82KCl + 2MnCl2 + 8KUO.<br />
The end-point of the reaction is sharp. If 5*27 grammes of pure<br />
potassium permanganate be dissolved per litre of solution, 1 c.c.<br />
will be equivalent to 1 per cent, of antimony with 1 gramme<br />
of the original sample.<br />
(y) H. Causse,* in Comptes Rendus, 1897, describes a new method<br />
for the volumetric estimation of antimony, which is based upon the<br />
fact that antimonious acid, free or combined, reduces iodic acid, with<br />
the formation of antimonic acid and the liberation of a proportionate<br />
amount of iodine, the reaction being thus :—<br />
5Sb2O3 + 4HIO3 = Sb2O5 + 41 + 2H2O.<br />
The solutions required are: iodic acid, 50 grms. in 250 c.c. ; decinorrnal<br />
sodium thiosulphate; 20 per cent, potassium iodide; and<br />
starch paste. Into the flask of a Fresenius or Mohr's iodometric<br />
apparatus, 0*5-0*6 gramme of antimonious oxide is weighed, 20-25<br />
c.c. of iodic acid are added, and 10 c.c. of potassium iodide solution<br />
are placed in the condensing apparatus. The contents of the flask are<br />
boiled until colourless, and the collected iodine determined with<br />
thiosulphate. From antimony compoxmds the sulphide is precipitated<br />
by sulphuretted hydrogen, then dissolved in HC1, and the oxide<br />
obtained by ffie action of sodium carbonate. The halogen acids,<br />
sulphurous acid, and sulphuretted hydrogen must be dissolved in<br />
* Taken from Mineral Industry.