The analysis of silver varies accord ing to its nature and combinations. Na tive silver, after being broken down and washed, is rubbed with liquid rhercury, which by strong trituration dissolves and combines with the silver. This amalgam is subjected to pressure, to separate, the excess of mercury. It is then distilled, and afterwards heated in a crucible to volatilize the mercury, and the silver remains pure. When silver is combined with antimony and sulphur, the ore is to he strongly roasted, to separate the antimony or sulphur. It is then melted with a proper quantity of alkaline flux. The sulphurated oxide of silver and anti mony may be treated in the same way.
See ASSATINO, Silver is of a fine white colour and great brilliancy. The Specific gravity is 10.4, and according to some, when it is hammered, 10.5, and sometimes nearly 11. The hard ness of silver is intermediate between iron and gold. The elasticity of silver is consi derable, and it is one of the most sonorous of the metals. It possesses very great duc tility and malleability. It may be beaten out into leaves of t of an inch thick, rrertf 151S and a grain of silver may be so extended, as to be formed into a hemispherical ves sel of sufficient capacity to hold an ounce of water, or to be drawn out into a wire four hundred feet in length. The tena city of silver is very great. A wire .078 of an inch in diameter will support a weight of one-hundred and eighty-seven pounds avoirdupois. Silver is a good con ductor of caloric. Its expansive power is less than that of lead and tin, and great er than thatof iron. When it is exposed to a white heat it melts. The tempera ture necessary to bring it to fusion has been calculated at the 1000° of Fahren heit; but, according to Kirwan, it re quires a higher temperature than 28° Wedgewood to melt it, although at that temperature it continues in a state of fu sion. When it is cooled slowly after fu sion, it exhibits some marks of crystalli zation. It assumes the form of four-sid ed pyramids or of octahedrons. If the heat be increased after the silver is melt ed, it boils, and may be reduced to va. pour. The surface of melted silver is so extremely brilliant, that it seems to throw out sparks, which is called coruscation by the workmen. Silver is a good conductor of electricity. It has no perceptible taste or smell.
Silver is not altered by exposure to the air, although it is soon tarnished, which is owing, as Probst ascertained, to a thin covering of suiphuret of silver, which is formed by sulphureous vapours to which it is exposed ; but when it is subjected to a strong heat for a long time, in an open vessel, it combines with the oxygen of the atmosphere, and is converted into an oxide. In the experiments of Macquer,
the oxydation of silver was effected by exposing it for twenty times successively, in a crucible, to the strong heat of a porcelain furnace. At last perceptible traces of oxydation were observed, and a vitreous matter of an olive colour was oh. tained. In other experiments silver being acted on by the heat of a burning-glass was covered with a white powder, which was afterwards converted into a crust of a green colour. Van Marum passed elec tric shocks through silver wire, which was instantly reduced to a kind of pow der, with a greenish white flame, and the oxide which was formed was dissipated in vapour. The oxide of silver, which is formed by these processes, is of a greenish or yellow colour. It is compos ed of about ten parts of oxygen, and ninety of silver. The oxide of silver is very easily reduced, for the affinity of ox ygen for this metal is very feeble. It is decomposed by the application of heat, and even when it is exposed to the light. By heating it in close vessels, pure oxy gen gas is obtained, and the metal is con verted to the metallic state, by melting it in a crucible.
Silver combines with phosphorus, form ing a phosphuret. One part of silver in filings, with two of phosphoric glass, and half* part of charcoal, exposed to heat in a crucible, yielded a phosphuret of silver, which had acquired one-fourth of its primitive weight of silver. This phos phuret is of a white colour, brittle, of a granulated texture, and may be cut with a knife. By throwing pieces of phos phorus on silver red hot in a crucible, the metal is instantly melted, and the phosphuret which is formed remains at the bottom. At the moment when the surface becomes solid, a quantity of phosphorus is thrown out with a kind of explosion, and the surface of the metal then exhibits a mamellated appearance. Pelletier, who first made this experi ment, concludes from it, that silver is susceptible of retaining a greater pro portion of phosphorus,. in combination with it, when it is in fusion, than in the solid state, and that the separation of the phosphorus is owing to the sudden con traction of the silver. A hundred parts of silver in fusion retain twenty-five of phosphorus, but only fifteen when it be comes solid.