Section I.—Of the Chemical History and Tests for the preparations of Antimony.
Metallic antimony has a bluish-white colour, not liable to tarnish. Its specific gravity is 6·7. It is easily fused, but is not very volatile. In certain circumstances, however, it easily undergoes a spurious sublimation, by being carried along with gases disengaged while it is in the act of being reduced.
A great number of preparations of antimony were at one time to be found in the shop of the apothecary; but they are now reduced to a few. Those which require notice here are the oxide, chloride, and tartar-emetic.
The oxide [sesquioxide] is a white heavy powder, which is best known by its solubility in tartaric acid, and the effects of the tests for tartar-emetic on the solution.
The chloride [sesquichloride], as usually seen, is a yellow or reddish liquid, but when pure is colourless. It is highly corrosive. It is readily known by the effect of water in decomposing it,—an insoluble white subchloride being thrown down, and hydrochloric acid remaining in solution. The latter is detected by nitrate of silver; and the precipitate is known by being soluble in a solution of tartaric acid, and then presenting the reactions of tartar-emetic.
Tartar-Emetic.
In its solid state tartar-emetic forms regular tetraedral or more generally octaedral crystals, which are colourless when pure, efflorescent, and of a slightly metallic taste. As commonly seen in the shops it is in the form of a white, or pale yellowish-white powder.
When heated it decrepitates and then chars; and if the heat be increased the oxide of antimony is reduced by the carbonaceous matter, and little globules appear, like those of quicksilver in point of colour. The best way of reducing tartar-emetic is to char it in a porcelain vessel or watch-glass, and then to increase the heat till the charred mass takes fire. Or the charred mass may be introduced into a tube and heated strongly with the blowpipe, after which globules of antimony will be found lining the bottom of the glass where the material has been. None of it is ever sublimed. It is not easy to procure distinct globules by heating tartar-emetic at once in a small tube.
According to Dr. Duncan, tartar-emetic is soluble in three parts of boiling and fifteen of temperate water. The solution presents the following characters with reagents.
1. Caustic potass precipitates a white sesquioxide, but only if the solution is tolerably concentrated. The first portions of the test have no effect. The precipitate is redissolved by an excess of potass.