ZINC. This metal, in commerce frequently called Speller, does not occur in the native state, but is obtained from its ores, which are chiefly the sulphuret and carbonate of zinc. Zino has a brilliant metallic lustre and a bluish white colour. It is so hard as to be filed-with some difficulty, and its toughness is such as to require very considerable force to break it when the mass is considerable. The specific gravity of zinc varies from 6.80 to 7.21. It undergoes little alteration, even by the combined operation of air and moisture, at common temperatures. When heated to between the temperature of boiling water and 300° Fahr., it becomes both malleable and ductile, so that it may be rolled into sheets and drawn into wire. It fuses at 773°Fahr., and when cautiously cooled crystallises, as suming the prismatic form. Exposed to a white heat, out of the contact of air, it sub limes and is condensed unchanged.
The ores of zinc comprise the Sulphuret, or Bknde ; the Oxistriphuret, or Voltzite ; the Carbonate, or Calamine; the Hydrous Car bonate; the Sulphate; the Phosphate; the Silicate ; the Hydrous Silicate ; the Alumi nate ; the Oxide of Zinc and Manganese; the Sulphuret of Zinc and Iron. Some of these
ores are crystalline, some massive. The largest specimen ever procured, perhaps, is that which has been sent from America to the Great Exhibition, and which weighs 10,000 11A Tho combinations of zinc with other sub.. stances are numerous, and many of them valuable. The Sulphate of Zinc constitutes While Vitriol. Zino combined with copper formi Brass; and iyith iron it forms a very hard alloy. If plates of hot iron be dipped into melted zinc, they acquire the appearance of tin-plate, and the iron is prevented from rusting; the coating of zinc is sometimes applied by galvanic agency.