SILVER. — Silver (argentum) in its pure metallic state has a perfectly white color and a high degree of lustre. It is unaffected by oxygen or moisture, but is readily attacked by sulphur, and tarnishes when exposed to the air containing hy drogen sulphide. The metal is not offi cial, though some of its salts and the oxide are. Of official preparations of silver, the nitrate is most largely used.
Cyanide of silver (argenti cyanidum, U. S. P.) occurs as a white, odorless, and tasteless powder, which turns dark upon exposure to the light. It is soluble in potassium cyanide, ammonia, boiling di lute nitric acid, and in sodium thiosul phate. It is used for making the official dilute hydrocyanic acid, and is rarely used internally.
Iodide of silver (argenti iodidum, U. S. P.) occurs as a light-yellow, odorless, and tasteless powder, which is unaffected by the light, if pure. It is soluble in a solution of potassium iodide or cyanide, and in ammonium thiosulphate.
Nitrate of silver (argenti nitras, U. S. P.) occurs in colorless and odorless rhom bic plates, having a bitter, caustic, metal lic taste, and is rapidly reduced by or ganic matter when exposed to the light. It is soluble in 0.6 part of cold and 0.1 part of boiling water, in 26 parts of cold and 5 parts of boiling alcohol. It is in compatible with organic matter, hydro chloric acid, chlorides,. phosphates, ar senitcs, opium, extracts, resin, essential oils, tannin, etc. It should be carefully preserved from light and air. The crys tals are alone suited for internal use. For external use two preparations of the nitrate are official: the fused and the diluted nitrate.
Fused nitrate of silver (molded silver nitrate; lunar caustic; argenti nitras fusus, U. S. P.) is prepared by melting crystals of silver nitrate with 4 per cent. of official hydrochloric acid and running the resultant liquid into suitable molds. It occurs in white, hard, odorless, solid pencils or cones, having a fibrous fract ure, and a bitter, metallic, caustic taste. It becomes gray or grayish black upon exposure, and is soluble in water, alcohol, nitric acid, etc.
Diluted nitrate of silver (mitigated stick; mitigated lunar caustic; argenti nitras dilutus, U. S. P.) is prepared by melting 1 part of silver-nitrate crystals and 2 parts of potassium nitrate. It oc
curs in white sticks and cones, is soluble in water, and is intended for external use where pure lunar caustic is too powerful.
Oxide of silver (argenti oxidum, U. S. P.) occurs as a heavy, odorless, brownish black powder, having a disagreeable, me tallic taste. It is incompatible with am monia-water, creasote, tannin, acids, etc. It should not be triturated with oxidiz able matter, as it may cause explosion. It is best dispensed mixed with some
Preparations and Doses.—Argenti cy auidum (U. S. P.), to 1/20 grain.
Argenti iodidum (U. S. P.), V, to 2 grains.
Argenti nitras (U. S. P.), to grain.
Argenti nitras dilutus, U. S. P. (miti gated caustic).
Argenti nitras fusus, U. S. P. (lunar caustic).
Argenti oxidum (U. S. P.), to 2 grains.
Physiological Action. of sil ver coagulates albumin, and, when ap plied in its pure state to living tissues, coats them over with a tough, white film (albuminate of silver) and acts as a caustic. This caustic action is not, how ever, a deep one, because the tough film which is formed acts as a protective. In dilute solution its action is astringent, overcoming relaxation and constringing the vessels, and apparently alterative, im proving local nutrition.
Taken internally in medicinal doses, silver nitrate acts as a tonic to the nerv ous system, causes changes in the blood, stimulates the heart, and promotes con structive tissue-metamorphosis and in creases the secretion of the bile. Large doses, by reason of its caustic action, pro duce violent gastro-enteritis, thrombosis of the gastric veins, and ulceration of the mucous membrane of the stomach. On account of its affinity for organic matter, silver nitrate cannot long maintain its identity in the stomach. Bogolowsky (Virehow's Archiv, xlvi, 413) has ob served that, when silver nitrate is added to a peptone, it is readily dissolved, and that the solution formed does not co agulate albumin; that in this or in some analogous form silver is absorbed is proved by its having been found in vari ous internal organs and by the discol oration which follows its protracted use.