ZINCUM - ZINC, Zn,=65.

This mineral is obtained, for commercial purposes, mainly from two ores - the carbonate (calamine) and the sulphide (blende) - by distillation with carbon. It has been found also in plants which grow on the calamine hills of Rhenish Prussia. It is liable to contain arsenic, iron, copper, and sulphur. Alloyed with copper, zinc forms brass; with nickel, "German silver." It is extensively used in galvanic combinations, and forms the positive plate of many voltaic batteries; as a coating on iron (galvanized iron) it protects from oxidation. Granulated zinc is prepared by pouring the molten metal into cold water.

Characters And Tests

Zinc is a brittle bluish-white metal, which at a red heat burns with a brilliant flame, and emits white fumes of oxide; sp. gr. 7. It is the only metal which yields a white sulphide with sulphide of ammonium, and hence this reaction is the characteristic test for it. Fixed and volatile alkalies also give with zinc white precipitates, soluble in excess of the reagents.