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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THE ANALYSIS OF ANTIMONY COMPOUNDS. 181<br />
B. Quantitative.<br />
1. Dry Method.—Fire Assaying.—Dr J. Clark says (Journ. Soc.<br />
Chem. Ind., 1896) that fire-assay for antimony ore is inaccurate, and<br />
refers to Carnot's investigation upon the same subject (Annales des<br />
Mines, vol. L), wherein it was shown that results were rarely within<br />
8 or 9 per cent, of the truth.<br />
In assaying antimony ores it is necessary to determine one of the<br />
following things:—<br />
(a) The pure sulphide of antimony (antimony crude) which the ore<br />
may contain.<br />
(/3) The metallic antimony (antimony regulus) which the ore may<br />
yield.<br />
(a) The Determination of the Sulphide of Antimony.—The ore is<br />
first broken into small pieced, which are then charged into a crucible<br />
with perforated bottom. This is fitted into a second crucible for about<br />
half its depth. The lid of the first crucible and the joint between<br />
the two crucibles should be luted with fire-clay and sand. Only<br />
the upper crucible is heated, while the lower one is allowed to pro<br />
trude into the ash-pit of the furnace. Thus the sulphide is melted<br />
and collects in the lower crucible.<br />
(/3) The Determination of Metallic Antimony.—<br />
1. The ore is in the oxide state:—<br />
Ore 10 grms.<br />
Soda(NaHCO8) . . ' . . . 25 „<br />
Argol 5 „<br />
Salt . . . . . . . cover.<br />
The heat must be carefully regulated, and the assay should be<br />
taken off the fire as quickly as possible.<br />
2. The ore is a sulphide or an oxide :—<br />
Ore 10 grms.<br />
Cyanide of potassium . . . . 35-40 ,,<br />
Salt . . . . . . . cover.<br />
The heat applied must be low, and the operation must be a quick one<br />
The button obtained should be cleaned^ by washing only, and not<br />
by hammering, as it is brittle. The button could be tested for iron<br />
or other impurities present. The foreign metals can be separated<br />
by treating the broken button with concentrated nitric acid, which<br />
converts the antimony into an antimonic acid precipitate. Filter,<br />
wash, dry, and ignite. The weight multiplied by 0'790067 gives<br />
the metallic antimony. Often this step is unnecessary, as the
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