ZINC; in chemistry and mineralogy, a metal unknown to the ancients,though they were acquainted with calamine, one of its ores, and the effect which this had in con verting copper into brass. Zinc has usu ally been ranked among those metals, which, from their imperfect ductility and malleability, were long denominated semi metals. It was known, that by uniform pressure zinc might be extended into thin plates, and more lately, it has been dis covered, that, at a certain temperature, it has so much malleability and ductility, that it can be lamellated, and drawn into wire. For this invention a patent has been obtained by Messrs. Hobson and Sylvester, to the latter of whom this work has been indebted for certain articles. See the PREFACE.
temperature at which zinc pos sesses these properties is between 210° and 300° of Fahrenheit, and by keeping it in an oven at this heat, it may readily be extended. By annealing, it retains this tenacity as to be easily bent. At a higher temperature it is brittle, so as to fall to pieces under the hammer. Zinc is of a white colour, with a shade of blue ; in a fresh fracture it is possessed of considera Me lustre. It is hard, and not easily cut with a knife. The specific gravity is nearly 7.2. The ores of zinc are cala mine and blende. See CALAMINARIS. Ca lamine is an oxide, frequently with a por tion of carbonic acid ; blende is a sulphu ret, containing also some iron, and other extraneous matters. The ores of zinc are found in many countries, and in a number of mines in this country. The metal is obtained from the ore by distillation.
Zinc is melted by a moderate heat, and the fused mass, on cooling, forms regular crystals. Though scarcely altered by ex posure to the air at a low temperature, yet it is rapidly oxydized by one amounting to ignition. When kept in a degree of heat barely sufficient for its fusion, zinc, becomes covered with a grey oxide. But when thrown into a crucible, or deep earthen pot, heated to whiteness, it sud denly inflames, burns with a beautiful white flame, and a white and light oxide sublimes, having a considerable resem blance to carded wool. This oxide, how ever, when once deposited, is no longer volatile ; but, if exposed to a violent heat, runs into glass. Zinc readily dissolves in sulphuric, nitric, and muriatic acids. With nitric acid, it yields nitrous gas, if the acid be concentrated ; or nitrous oxide, if diluted. Sulphuric and muriatic acids, diluted with water, evolve, during their action on this metal, hydrogen gas ; and the gas, when obtained, holds in combi nation a portion of the metal. A stream of it has been found, if recently prepared, to occasion the fusion of the platina wire, though the pure gas is destitute of this property. This hydrogen gas, holding zinc in solution, may also be obtained by a process of Vauquelin. A mixture of the ore of zinc, called blcnde, or calamine, with charcoal, is to be put into a porce lain tube, which is to be placed horizon tally in a furnace, and, when red-hot, the vapour of water is to be driven over it. The gas that is produced, however, is a mixture of carbonic acid, carburetted hy drogen, and hydro-zincic gas. The zinc is deposited on the surface of the water, by which this gas is confined ; but, if burned when recently prepared, the gas exhibits, in consequence of this impreg nation, a blue flame. The solution of
zinc in sulphuric acid shoots into regular crystals. This salt is readily soluble, and Its solution is not precipitated by any other metal. The muriate of zinc yields, when evaporated, an extract of thick consistence, having the viscidity of bird lime. 'dine is oxydized also, when bulled with solutions of pure alkalies; and a por tion of the oxide is retained in solution. It is oxydized when mixed with nitre, and projected into a red-hot crucible. In this case a violent detonation ensues.
Zinc combines with almost all the me tals, and some of its alloys arc of great importance It may he united to gold in any proportion by fusion. The alloy is the whiter and the more brittle, the greater quantity of zinc it contains. An alloy, consisting of equal parts of these metals, is very hard and white, receives a fine polish, and does not tarnish readily. It has therefore been proposed as very proper for the specula of telescopes. One part of zinc is said to destroy the ductility of one hundred parts of gold. Platinum combines very readily with zinc. The alloy is brittle, pretty hard, very fusible, of a bluish-white colour, and not so clear as that of zinc The alloy of silver and zinc is easily produced by fu sion. It is brittle, and has not been applied to any use. Zinc may be combined with mercury, either by triturating the two metals together, or by dropping mercury into melted zinc. This amalgam is solid. It crystallizes when melted, and cooled slowly into lamellated hexagonal figures, with cavities between them. They are composed of one part of zinc, and two and a half of mercury. It is used to rub on electrical machines, in order to excite electricity.
Zinc combines readily with copper, and forms one of the most useful of all the me tallic alloys. The metals are usually com bined together by stratifying plated of copper, and a native oxide of zinc com bined with carbonic acid, called calamine, and applying heat. When the zinc does not exceed a fourth part of the copper, the alloy is known by the name of brass. It is of a beautiful yellow colour, more fusible than copper, and not so apt to tar nish. It is malleable, and so ductile, that it may be drawn out into wire. Its density is greater than the mean. It ought to be by calculation 7.6, but it actually is 8'.4 nearly, so that its derisity is increased by about one-tenth. When the alloy contains three parts of zinc and four of copper, it assumes a colour nearly the same with gold, but it is not so malleable as brass. It is then called pinchbeck, prince's me tal, or Prince Rupert's metal. Brass was known, and very much valued, by the ancients. They used an ore of zinc to fbrm it, which they called cadmic. Dr. Watson has proved that it was to brass that they gave the name of orichalcum. Their xs WaSS copper, or rather bronze.
It is very difficult to form an alloy of iron and zinc. Malouin has shown that zinc may be used instead of tin to cover iron plates, a proof that there is an affi nity between the two metals. Tin and zinc may be easily combined by fusion. The alloy is much harder than zinc, and scarcely less ductile. This alloy is often the principal ingredient in the compound called pewter.