Nitrate of Silver, AgNO3; Ag, 63·51 per cent., N2O5, 36·49 per cent. This salt is either sold crystallised in colourless rhombic prisms, or in the form of small white pencils or sticks. It gives the reactions for silver and nitric acid, and stains the skin black. 100 parts, dissolved in distilled water, should give, with hydrochloric acid, a precipitate which, when washed and dried, weighs 83·4 parts. The silver is, however, far more quickly estimated by the blowpipe than in the wet way. One grm. fused in a cavity on charcoal should give a little globule of metallic silver, weighing about ·6351 grm. The chief adulterations of this substance are copper, lead, and nitrate of potash. If all the silver is precipitated by hydrochloric acid, carefully filtered off, and the filtrate evaporated to dryness, any residue will denote adulteration or impurity.
Argenti Oxidum, Oxide of Silver, Ag2O = 232; Ag, 93·19 per cent.—A dark olive-brown powder, soluble in ammonia and nitric acid. By ignition it readily yields metallic silver. The P.B. directs that 29 grains of the oxide should yield 27 of metallic silver.
Nitrate of Silver and Potash (Argentum nitricum cum kali nitrico), AgNO3 + KNO3.—This preparation is in most of the pharmacopœias, Austrian, German, Danish, Swedish, Russian, Swiss, and the British; it is directed by the B.P. to be composed of 1 part of silver nitrate and 1 part of potassic nitrate fused together. A “toughened silver nitrate” is made by fusing together potassic nitrate 5, silver nitrate 95. Mild caustic points are used by oculists by fusing 1 of silver nitrate with 2, 3, 31⁄2, and 4 parts of potassic nitrate.
(2) Silver in the Arts.—The uses of the metal in coinage, articles for domestic purposes, for ornament, &c., are too well known to require enumeration. The only forms in which silver is likely to give rise to accident are the salts used in medicine, photography, in the dyeing of hair, and in the manufacture of marking inks.
Hair-dyes.—About one-half of the hair-dyes in use are made with nitrate of silver. The following are only a few of the recipes:—
Aqua Orientalis.—Grain silver 2 drms., nitric acid 1 oz., steel filings 4 drms., distilled water 11⁄2 oz.—the whole finally made up to 31⁄2 fluid ozs., and filtered.
Argentan Tincture.—Nitrate of silver 1 drachm, rose water 1 fluid oz., sufficient nitrate of copper to impart a greenish tint.
Eau d’Afrique.—Two solutions—one of nitrate of silver, the other of potash, containing ammonium sulphide.
The photographer uses various salts of silver, the chief of which are—the nitrate, iodide, bromide, cyanide, and chloride of silver.
Marking Inks.—Some of the more important recipes for marking ink are as follows:—