ZINC. See CHEMISTRY, p. 1884, sect. iii. 8.; MATERIA MEDICA, Catalogue of Simples; and PHARMACY, n° 798—801.
It is remarkable that this semi-metal, when united with copper even in a considerable proportion, diminishes very little the malleability of that metal, and at the same time renders its colour more beautiful, and more like the colour of gold. This colour varies according to the different proportions of these two metallic substances in the compound, which acquires different names accordingly, as brass, tombac, similor, pinchbeck, and prince's metal. The zinc for these compositions must be very pure, and free from other metallic bodies. The method of purifying this semi-metal, which is principally founded upon its property of not uniting with sulphur, is thus described by Mr Macquer:—When zinc is melted in a large crucible, fuet and sulphur alternately, and the latter in larger quantities than the former, must be thrown upon it. If the zinc is pure, the sulphur burns freely on its surface; but if it is assayed, the sulphur combines with the other metals, and forms with them a kind of scoria, which must be taken off. This alternate projection of fuet and sulphur upon zinc is continued till the sulphur be burnt on the surface of the melted zinc without forming any scoria; the zinc thus purified, may be successfully employed for making of brass or metallic mixtures in imitation of gold.