Different methods are followed for procuring the metal from the oxide. It is sometimes mixed with one half its weight of crude tartar, and exposed to a strong heat, in covered vessels, by which the oxygen of the oxide unites with the carbon of the acid of the tartar ; and the metal, in a state of fusion, falls to the bottom of the vessel. There is also formed a compound of the antimony with the sulphurct of potassa, which is ge nerated by the union of the alkali of the tartar with the sulphur contained in the oxide. The quantity of metal obtained by this process amounts to about 70 per cent. of the oxide employed, and 100 of the sulphuret yield about 70 of oxide.
Another method of procuring antimony, is by melting the oxide along with fat and charcoal. \Vhen the mix ture is in a state of fusion, nitre, in the proportion of about 1 oz. to the pound, is gradually added. The whole is then poured out, and allowed to cool. By this means more of the metal is procured than by the above process.
The third method of obtaining antimony, is by add ing some body as a metal, which unites with the sul phur. For this purpose iron is always employed. In decomposing the sulphuret in this way, 8 parts of iron, in small pieces, are heated to whiteness in a crucible; 16 parts of coarsely powdered sulphuret are then added, and the vessel is covered for a short time. \Vhen the
whole is in fusion, 3 parts of nitre are gradually thrown in, and the product, after a short time, is poured into greased cones, which must be gently struck from time to time, as the matter consolidates, to cause the metal to fall to the bottom. When the whole has become solid, about 10 parts of antimony are found in the ves sel, which, however, still retains iron and sulphur. To free it from these, it must be again melted with 3 parts of nitre, and 2 of sulphuret, which must be repeated twice before the antimony is obtained pure. From 18 of sulphuret 8 of metal are procured by this process.
Assay of the Sullihriret.
Sulphuret of antimony, besides sulphur and antimo ny. contains also lead, iron, copper, stony matter, and occasionally silver. The assay, with the view of as certaining the quantity of antimony, is, however, easily performed, by digesting the sulphuret in nitric acid. After the action has ceased, the solution is poured off, and the insoluble residue is dissolved in nitro-muriatic acid. To the solution, a large quantity of water is add ed, and the precipitate thrown down, is mixed with twice its weight of crude tartar and a little nitre, and exposed to heat, by which the antimony is obtained in the metallic state