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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136 THE METALLURGY OF ANTIMONY.<br />
At Banya the data are:—<br />
Charge for the furnace, impure antimony (high grade, Sb = 9O per cent.) 990 lbs.<br />
» (low grade, Sb = 74 „ ) 110 „<br />
Sodium sulphate added 92-6,,<br />
Powdered charcoal . . . . . . • • . . 11 ,,<br />
Raw ore . . . 330 ,,<br />
After ten hours the slag is drawn off, and the materials to form the<br />
star slag are added :—2*2 lbs. of crude antimony, 13*2 lbs of roasted<br />
sulphide of antimony, 7 # 5 lbs. of potash, and 5*7 lbs. of soda ash. The<br />
following gives the analysis of the impurities found in the refined<br />
star antimony thus obtained :—<br />
Arsenic 0*330 per cent.<br />
Iron 0-052 ,,<br />
Silver 0'006 ,,<br />
Sulphur . . . . . 0720 ,,<br />
Total . . . 1*108<br />
At Siena, where the unrefined metal is less impure, the following<br />
shows the proportions in 260 charges:—<br />
Unrefined metal . . . . 115,255 lbs.<br />
Salt 27,229 ,,<br />
Roasted ore . . . . ' . 767 „<br />
Refinery slag 12,549 ,,<br />
Refined antimony obtained, 107,697 lbs., which is equal to 93-5 per<br />
cent.<br />
Antimony contains small quantities of iron, lead, sulphur, arsenic,<br />
etc., as impurities.<br />
In order to produce an almost absolutely pure antimony, Liebig's<br />
process may be used. Mix powdered antimony with one-eighth of its<br />
weight of carbonate of sodium and one-sixteenth of its weight of<br />
sulphide of antimony, and heat the mixture in a Hesse crucible. The<br />
button thus obtained is submitted to another fusion with carbonate of<br />
sodium only for two hours, and to a third fusion with a mixture of<br />
carbonate of sodium to which a small quantity of potassium nitrate has<br />
been added. In these operations the sulphur of the antimony sulphide<br />
transforms the foreign metals present, except lead, into sulphides,<br />
which remain in solution in the scoria; the arsenic compounds pass<br />
in part to the sulpho-arsenate of soda and in part to the state of<br />
arsenate. The addition of potassium nitrate removes the last trace<br />
of arsenic by .converting it into arsenate of soda.<br />
The Products of Kenning.-—The products of refining are refined<br />
antimony, slag and star slag.