Zinc Chloride, , formerly known as Butter of Zinc, is formed by heating the metal in chlorine gas. But it is usually obtained by dissolving zinc or its oxide in hydrochloric acid, and evaporating the solution to dryness, fusing the residue, and casting it into cakes. When thus prepared it contains some oxychloride. It is grayish white, waxy, and extremely hygroscopic. It is very soluble in water, for which it has a great affinity, and is used as a caustic. Chloride of zinc deprives some organic bodies of water, producing decomposition. It is disinfectant and antiseptic.
ORES.—Blende and Calamine are the two principal ores of zinc. Those of minor importance are Zincite, Frankinite (q.v.), and Electric Calamine.
Blende, Sphalerite, Black Jack, or Sulphide of Zinc, contains when pure 67 per cent. of zinc and 33 of sulphur, but like most ores it usually contains impurities. It crystallises in the tetrahedron section of the cubic system. The crystals are generally of a beautiful black colour, and present considerable variety in their forms. Blende occurs in all the older geological formations sometimes associated with the ores of copper and tin, but most frequently with galena or sulphide of lead. In the United Kingdom blende is now chiefly mined in Wales, the Isle of Man, and Cumberland. It also occurs with galena at Leadhills in Scotland. On the Continent it is found plentifully in many localities, and abundantly in America with lead ore in Missouri, Wisconsin, Iowa, and
Illinois. Blende is associated with other minerals in many places in Australia, but has not yet been found in large quantity.
Calamine, or Carbonate of Zinc.—By some mineralogists this mineral is called Smithsonite, a name more usually given to the silicate of zinc. It crystallises in the rhombohedral system, and contains when pure 52 per cent. of zinc. Calamine is generally found in calcareous rocks, and is usually of a dull yellow or reddish-brown colour in the ordinary massive state. Owing to impurities of earthy matters and oxide of iron, its percentage of zinc is sometimes as low as from 15 to 20. Calamine and blende are frequently associated. The metal obtained from the latter is generally somewhat inferior. Carbonate of zinc occurs in Belgium, in Silesia, at Santander in Spain, and elsewhere; but little is now raised in England. In the United States it is plentiful at Lancaster, Pennsylvania, and also occurs in south-west Missouri, Minnesota, Wisconsin, and in Arkansas, where in Marian county a variety is found coloured bright yellow by sulphide of cadmium, and known locally as 'turkey-fat ore.'
Electric Calamine, Silicate of Zinc.—The composition of this mineral when pure is zinc-oxide 67.5 (zinc 54), silica 25.0, water 7.5. It crystallises in the orthorhombic system, and its crystals are strongly pyro-electric. Its colour, always delicate, has many shades, such as white, blue, green, brown, yellow, red, and gray. Electric calamine is found along with other zinc or lead minerals in Carinthia, Westphalia, near Aix-la-Chapelle, and sparingly at Matlock and elsewhere in England. It is worked at one or two places in the United States, notably near Selinsgrove on the Susquehanna, and in Wythe county, Virginia. Silicate of zinc is now more easily smelted than formerly through the introduction of Siemens' gas-furnace.