i, Chimney.
Prep. Native antimony is freed from impurities by fusion. The sulphide, after being melted from the gangue, is commonly oxidised by exposure on the concave hearth of a reverberatory furnace, and is then reduced to the metallic state by fusion in crucibles with coal-dust, crude tartar, or some other deoxidising agent. To free the product from iron, it is generally fused, or re-fused, with a little antimonic oxide; and when the ore contains arsenic, iron, or its oxide, and an alkaline carbonate or sulphate, are used in the same way. It is seldom prepared on the small scale. The following formulæ are in use, or are recommended:—
1. On the SMALL SCALE:—
a. From tersulphide of antimony, in coarse powder, 2 parts; iron filings, 1 part; fused together in a covered crucible, at a heat gradually raised to dull redness.
b. From the teroxide or the oxychloride of antimony, fused together, as before, with twice its weight of crude tartar.
c. (Ph. Castr. Ru. 1840.) Sulphide of antimony, 16 parts; cream of tartar, 6 parts; both in powder; throw the mixture, in small quantities at a time, into a vessel (an earthen crucible) heated to redness; when the reaction is over (having closely covered the vessel), fuse the mass, and after a quarter of an hour pour it out, and separate the metal from the slag.
d. From sulphide of antimony, 8 parts; crude tartar, 6 parts; nitre, 3 parts; as last.
e. (Wöhler.) Sulphide of antimony, 10 parts; nitre, 12 parts; dry carbonate of soda, 15 parts; deflagrate together; powder the resulting mass, and wash it thoroughly with boiling water; lastly, smelt the dried residuum with black flux. All the preceding are nearly pure; the impurity, if any, being traces of copper, lead, or iron.
f. (Berzelius.) From metallic antimony, in fine powder, 2 parts; teroxide of antimony, 1 part; fused together. The product will be pure provided the antimony employed is free from lead.
g. (Muspratt.) From antimony, 9 parts; peroxide of manganese, 1 part; fused together; the resulting metal being re-fused with 1-10th of its weight of carbonate of soda.