Zinc is a blueish white metal, having a specific gravity of 6.8 to 7.2; tough when cold, ductile and malleable at from 250° to 300° Fahr., brittle and easily pulverized at 500°; fuses at 773°, and sublimes unchanged at a white heat, in close vessels. It is scarcely affected by exposure to air and moisture; hence its general use in the arts for the manufacture of vessels of capacity, tubing, etc., that require lightness and durability. Acids, even diluted, attack zinc rapidly. It is also soluble in caustic alkalies. Heated to whiteness, 941° Fahr., in contact with the air, it burns with great brilliancy, and is converted into oxide, (flowers of zinc). It is very soluble in dilute sulphuric and muriatic acid, with the evolution of hydrogen gas. The salts of zinc are colorless.

Commercial zinc is never pure, and is obtained from the native sulphuret (zinc blende) or carbonate (calamine), by roasting those. ores, and distilling them along with carbon- ' aceous matter in a covered earthen crucible, having its bottom connected with an iron tube which terminates over a vessel of water situated beneath the furnace. The first portion that passes over contains cadmium and arsenic, and is indicated by what is technically called the brown blaze; but when the metallic vapor begins to burn with a blueish white flame, or the blue blaze commences, the volatilized metal is collected. Zinc may be alloyed with most of the metals. (Cooley.)

3311. Purification of Zinc

3311.    Purification of Zinc. Granulate zinc by melting, and pouring it, while very hot, into a deep vessel filled with water. Place the granulated zinc in a Hessian crucible, in alternate layers, with one-fourth its weight of nitre, with an excess of nitre at the top. Cover the crucible, and secure the lid; then apply heat. When deflagration takes place, remove from the fire, separate the dross, and run the zinc into an ingot mould. It is quite free from arsenic.

3312. To Granulate Zinc

3312.    To Granulate Zinc. Granulated zinc is obtained by pouring the molten metal into a warm mortar and triturating vigorously, with an iron pestle, until it solidifies. (See No. 3311 (Purification of Zinc).)

3313. To Color Metals

3313.    To Color Metals. Make a solution of 4 ounces hyposulphite of soda in 11/2 pints of water, and add a solution of 1 ounce acetate of lead in the same quantity of water. Articles to be colored are placed in the mixture, which is then gradually heated to a boiling point. The effect of this solution is to give iron the effect of blue steel, zinc becomes bronze, and copper or brass becomes successively yellowish red, scarlet, deep blue, blueish white, and finally white with a tinge of rose. This solution has no effect on lead or tin. By replacing the acetate of lead in the solution with sulphate of copper, brass becomes of a fine rosy tint, then green, and finally, of an iridescent brown color. Zinc does not color in this solution, it throws down a precipitate of brown sulphuret of copper; but if boiled in a solution containing both lead and copper, it becomes covered with a black crust, which may be improved by a thin coating of wax. (See No. 3188 (Puscher's Solution for Coloring Metals).)