properties of zinc.

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transparency. This zinc ore is contaminated with iron, lead,argillaceous and siliceous earths, kc. It occurs both in amor-phous masses and crystallized in a diversity of polygonal figures.

PROPERTIES OF ZINC.

Zinc on its fracture appears of a shining white colour, w'ith abluish tint. It possesses some degree of ductility and may beextended when carefully passed between metallic cylinders ina flatting mill. Its specific gravity is 7.190. It melts atFahr. By a farther increase of heat it is volatilized withoutchange. When melted in contact with the air, its surface be-comes covered w’ith an imperfect oxid; when heated a littleabove ignition it burns with a bright yellowish white flame,slightly tinged with green, and a white oxid is formed in lightflakes, which are carried off by the rapid current of air in theburning metal. It undergoes very little alteration from the air,its surface becomes slightly tarnished. It is not acted on bywater at the usual temperature of our atmosphere; but at that ofignition, it decomposes this fluid rapidly. It is oxidated and dis-solved by the greater number of the acids. It has a very strongattraction for oxigen, and therefore precipitates the greater num-ber of the metals from their acid solutions. All the alcalis whendigested or boiled w'ith zinc blacken its surface and dissolve aminute portion of it. It decomposes muriate of ammonia, sul-phate of potash, and various other neutral salts. A mixture ofnitrate of potash and zinc detonates with rapidity. Sulphur andzinc cannot be united by fusion. Gold, silver, platina, andnickel form brittle compounds with zinc. It easily unites withmercury and tin. It does not combine with lead or bismuth.The most frequent and at the same time most useful combinationof zinc is that with copper. It unites with great difficulty toarsenic, iron, and cobalt. It inflames in oxigenated muriaticacid gas, and fulminates by pressure or a blow with oxigenatedmuriate of potash. It is a very strong conductor of galvanism.

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