Lond. Edin. Dub. Silver.

Syn. Argent (F.), Silber (G.), Silwer (Swed.) Argento (I.), Plata (S.), Villie (Tarn.), Rupah (H.), Fezzeh (A.), Nokra (Pers.), Perak (Malay), Peddie (Cyng.), Rajata (Sans.), Im-root (Esquimaux), N'zurfa (Timbuctoo).

Silver exists native, and mineralized, in different parts of the globe: in Great Britain, in combination chiefly with lead; in France, native silver is found in the departments of the Isere and Haut Rhin; in Germany, the most important mines are those of Freyberg, Schneeberg, and the Harz1: mines of silver also exist in Norway and in Spain. Silver has likewise been found at Barnaoule in western Siberia, but not in any very great abundance. The most abundant mines are those of Peru and Mexico. It is found,

1 These yield annually 1530 marks of silver.

Besides these ores, there are many metallic ores which contain silver in sufficient quantity to render the extraction of it profitable. In its native state, it is in small lumps, or crystallized in cubes, hexahedrons, octahedrons, or dodecahedrons; and occasionally assumes the form of leaves, threads, or twigs.1 Its colour is white, its lustre metallic, and fracture hackly. Its specific gravity is from 10 to 10.338. It is not perfectly pure, but contains from .03 to .05 of gold, or arsenic, or antimony. But silver is obtained in its pure metallic state, generally, either by fusion or by amalgamation. By the first process, the native ore is roasted to expel the sulphuret, antimony, arsenic, or other volatile principles : the residuum is then fused with lead, and exposed in a cupel (a vessel made of bone or of wood ashes) to a strong heat in the hearth of a refining furnace; when the lead and the foreign metals, being thus oxidized, and the oxides fused, are in part absorbed by the porous cupel, and in part volatilized and driven off by the current of air from the bellows or the blast-pipe. An experienced eye knows when the silver is sufficiently pure; but in general it requires a second cupellation at a higher temperature to purify it completely from the lead with which it is combined.

By the second process, the ore is first roasted, then ground to a fine powder, washed, mixed with sea salt, and roasted in a reverberatory furnace. The sulphur is changed into sulphuric acid, and sulphate of soda is formed, whilst the chlorine of the sea salt forms with the silver a chloride. The whole roasted mass is next ground to powder, mixed with mercury, iron, and water, and formed into an amalgam with the mercury, by the barrels being made to revolve very rapidly on their axis by means of machinery. The silver is first separated from the chlorine by the iron, and forms an amalgam with the mercury : it is then separated from the mercury by distillation. For pharmaceutical purposes, the best mode of procuring pure silver is the following, pointed out by M. Gay Lussac:-Dissolve the silver to be purified in nitric acid, and dilute the solution with distilled water; then precipitate the silver by means of a clean plate of copper; wash the precipil It is found in this form in the famous mine of Potosi, and is called dendrites.

tate with a solution of nitrate of silver, digest in ammonia, and ultimately wash with boiling distilled water : the pure silver is then obtained in the state of powder. Or decompose the solution of the silver in nitric acid with muriate of soda, wash and dry the precipitate, and then throw the dry chloride in successive portions into a red-hot Hessian crucible containing carbonate of potassa, twice the weight of the chloride. Effervescence takes place, chloride of potassium is formed, carbonic acid and oxygen gas evolved, and pure silver subsides to the bottom of the crucible.

Qualities.-Pure silver is a brilliant-white, insipid, inodorous, sonorous metal, with a very rich lustre, which it loses when long exposed to the air, owing to sulphuretted hydrogen being almost always present in the atmosphere. It is in hardness between iron and gold, of considerable malleability, the finest silver leaf being only one third thicker than gold leaf. It is of inferior ductility to gold, platina, and iron. Its specific gravity, when hammered, is 10.51. Silver is fusible at 187° Fahr. or 28° Wedgewood; it is volatilized by a stronger heat; but difficult of oxidizement by the action of heat and air. It is oxidized by sulphuric and nitric acids, and combines with them; but none of the compounds, except that produced with the nitric acid, are used in medicine. In the solution of the nitrate chloride of sodium throws down a white precipitate, which is soluble in an excess of ammonia; -when the silver is pure, the addition of hydro-sulphuric acid does not colour the supernatant fluid.

The equivalent of silver is 108.

Medicalproperties and uses.-Metallic silver has no action on the human body; but when combined with cyanogen or nitric acid, it forms a very powerful remedy. Many of the instruments used by the surgeon require to be made of silver.

Officinal preparation. Argenti Nitras, L. E. D. Argenti Cyan-idum, L.