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

THE METALLUKGY OF ANTIMONY. 125
metal arid alkaline-earfch metal sulphides. The resulting reaction is
the production of a solution of soluble thio-antimonates, Na3SbS4
or Ca3(SbS4)2J and thio-antiinonites, Na3SbS3 or Ca3(SbS3)2. These
solutions can be electrolysed with the greatest ease.
The results of the experiments made by Borchers in 1886 prove
that antimony was deposited in equal quantity both from the thioantimoniate
and thio-antimonite. If a sodium thio-antimonate
solution be used, it is only necessary to add either sodium sulphide
or sodium hydroxide, in such quantity that there is at least one
atom of sodium for every atom of sulphur, in order to prevent the
separation of sulphur at the anode. In other words, the action takes
place best when three molecules of sodium sulphide (Na2S) are present
for each molecule of antimony sulphide (Sb2S8).
The relative distribution of the elements before and after the
experiment is shown in the following table :—
Before electrolysis—
In form of salts, etc.
After electrolysis—
In metallic form .
In solution—
2'410 kgrm. NaSH .
1-202 ,, NaA .
1*491 ,, Na^Oa + SHoO
Antimony.
Kgvms.
2*440
2-437
2-437
Sodium.
Kgvms.
1-840
0*990
0*503
0-275
1-768
Sulphur.
K grins.
2-560
1-377
0-699
0-384
2*460
Oxygen.
Kgrm.
0*020
...
0-288
0-288
The loss of antimony (3 grms.) is so small that the precipitation
may be considered as practically quantitative. The loss of sodium
and sulphur is due to the fact that the solution clinging to the
antimony after the powder had been removed was not added to the
rest of the liquid.
The experiments, as carried out by Borchers, also show a peculiar
fact, that with the same expenditure of current the same quantity of
antimony is deposited, whether it exists in the solution as the
trivalent or as the pentavalent antimony.
Practical Working of the Electrolytic Process.—The sodium sulphide
solution in the conical iron vessels (figs. 55-58, a) is treated and
agitated by means of steam introduced through the steam-pipe b. As
soon as the solution is boiling, the finely divided ore is sprinkled into