TIN (symb. Sn, atomic weight 118,* spec. gray. 7.29) is a beautiful silvery-white metal, with a tinge of yellow, and a high metallic luster. It possesses a crystallized text ure, and may be obtained in well-formed crystals of the pyramidal or tetragonal system; and it is in consequence of this crystalline texture that a bar of tin, when bent, emits a creaking sound, termed the cry of tin (the Zinngeschrie, or tin-shriek of the Germans). Tin is a soft metal—being softer than gold—and is very maleable, and can be beaten out into very thin laminae, in which form it is known as tin-foil. At a temperature of about 212° Fahr: its ductility is considerable, but by no means remarkable, and it may be then easily drawn into wire, the tenacity of which is only moderate, as a wire with a diameter of 0.17 of an inch is broken by a weight of about 50 pounds. It is a tolerably good conductor both of heat and electricity, and when handled communicates a peculiar odor to the skin. It melts at atemperature of 442° Fahr. ; and at a higher temperature, if air be present, it becomes converted into the binoxide, and burns with a brilliant white light. At ordinary temperatures it is very slightly acted on by exposure to the air, or to moisture. With regard to the action of the ordinary acids on this metal, prof. Miller observes that " nitric acid of specific gravity 1.3 acts upon it violently, and produces an insoluble hydrated binox ide, known as metastannic acid; at the same time, owing to the decomposition of water, a considerable quantity of ammonia is formed, which enters into combination with the excess of acid. Strong hydrochloric acid, when heated upon tin, dissolves it graduallv, with extrication of hydrogen. Aqua regia, if not too concentrated, dissolves the metal, and converts it into bichloride. Dilute sulphuric acid is without action on the metal in the cold; but if the concentrated acid be boiled upon it, the tin becomes converted into sulphate, while sulphurous acid escapes. The hydrates of potash and soda act upon tin at high temperatures, hydrogen being evolved, while a soluble metastannate of the alkali is formed."—Inorganic Chemistry, 2d ed., p. 588.
There are two principal oxides of tin—viz., the protoxide (SnO) and the binoxid There is also a sesquioxide, Protoxicle of Tin, or stannous oxide (SnO), is obtained'as a white hydrate (2SnO,H20) by precipitating a solution of the protochloride of tin with an excess of carbonate of soda. The protoxide acts as a base, forming salts which are colorless, redden litmus, and are for the most part soluble in water, from which crystaline tin is deposited on an inserted mass of zinc, constituting the so-called tin tree. None of these salts are of any special importance. Binoxide of tin, or stannic oxide occurs native in the anhy drous form, crystallizing in square prisms, which are sufficiently hard to scratch glass, and generally of a brown color, from the presence of peroxide of iron or of manganese. In its artificially-prepared hydrated condition, it has the character of an acid, and according to its different modes of preparation, forms two remarkable varieties, known as stannic and metastannic acids. Afetastannic acid is prepared by the action of strong
nitric acid on tin, and occurs as a white, crystalline, insoluble mass, which, when dried in air, consists of but when dried at 212° Fahr., loses five molecules of water, and consists of By ignition, it becomes anhydrous, and of a pale straw color. In this form (in which it resembles the native binoxide in its properties), it is known in commerce as putty-powder, and is employed for polishing plate, and for giving whiteness and opacity to enamels. In the hydrated state, it is insoluble in hydro chloric or nitric acids, but is freely soluble in solution of potash or soda, forming salts Which are not crystalline, but may be obtained in a granular form. Metastannic acid, in its hydrate state, may be recognized by the beautiful golden yellow metastannate of tin which is formed when it is moistened with protochloride of tin. Stannic acid 21120) is procured by the addition of carbonate of lime or of baryta to a solution of bichloride of tin, when it falls as a gelatinous precipitate. Unlike metastannic acid, it is readily soluble in nitric and hydrochloric acids; and at a temperature of 284° Fahr. it is converted into metastannic acid. In combination with the alkalies, it forms stannates, which crystallize readily, and whose formula is The stannate of soda is largely used as a mordant by the dyer.
There are two chlorides of tin—viz., a protochloride and a bichloride. The prota chloride of tin, or stannous chloride may be obtained in a hydrated form dissolving the metal in hydrochloric acid, and evaporating the solution, when the salt.. crystallizes in prismatic needles, having the composition The hydrated protochlOride is extensively used as a mordant, and for deoxidizing indigo and the peroxides of iron and manganese, by the dyer and calico-printer; and in consequence of its deoxidizing or reducing powers, it is sometimes employed in analytical chemistry, especially in the determination of the quantity of mercury, since all the mercurial salts, when boiled with it, are decomposed, and yield their mercury in the metallic form. Bichloride of tin, or stannic chloride forms numerous double salts with the soluble chlorides; the compound of this nature which it forms with chloride of ammo nium is represented by the formula and is employed by the dyer under the technical term of pink salt. An impure bichloride, prepared by dissolving tin at a gentle heat in a mixture of nitric acid and sal-ammoniac, and known in the trade as nitromuriate of tin, or composition, is also largely used by dyers and calico-printers.
The sulphides of tin are three in number—viz., the protosulphide, the sesquisulphide, and the bisulphide. The bisulphide of tin (SnS,) may be obtained in the hydrated state, iu the form of a dingy yellow precipitate, by passing sulphureted hydrogen through a solution of a pesalt of tin. In the dry way, it is procured in the form known as Mosaic gold, which is insoluble in any acid, though soluble in aqua regia; and is employed in the arts to give an appearance of bronze to the surface of metals.