Argentum Purificatum. B.P. Refined Silver.

Pure metallic silver.

Impurities. - Gold, copper, and lead.

Test. - If ammonia be added in excess to a solution of the metal in nitric acid, the resulting fluid exhibits neither colour nor turbidity.

Preparation. Argenti Nitras.

Argenti Nitras, B. and U.S.P. Nitrate of Silver. Lunar Causti

AgNO,; 169.7.

Characters. - In colourless tabular crystals, the primary form of which is the right rhombic prism; or in white cylindrical rods.

Solubility. - It is soluble in distilled water, and in rectified spirit.

Reactions. - The solution gives with hydrochloric acid a curdy white precipitate, which darkens by exposure to light, and is soluble in solution of ammonia. A small fragment heated on charcoal with the blowpipe, first melts, and then deflagrates, leaving behind a dull white metallic coating.

Preparation. - By dissolving silver in nitric acid, evaporating and crystallising.

It is obtained in rods by fusing the crystals in a capsule of platinum or thin porcelain, and pouring the melted salt into proper moulds. Nitrate of silver must be preserved in bottles carefully stoppered.

Toughened nitrate of silver or 'toughened caustic' is formed by adding 5 parts of nitrate of potassium to 95 parts of the nitrate of silver before fusion.

Peeparations for which Nitrate of Silver is used. Argenti et Potassil Ultras.

Argenti Oxidum.

Impurities. - Nitrate of potassium, metallic impurities. Tests. - Ten grains dissolved in two fluid drachms of distilled water give with hydrochloric acid a precipitate, which, when washed and thoroughly dried, weighs 8.44 grains. The filtrate, when evaporated by a water-bath, leaves no residue.

Dose. - 1/6 to 1/2 grain.

Administration. - As an application to the eyes or injection it is used in solutions of various strengths, but an ordinary safe one is 2 grains to the ounce. When made into pill it must not be mixed with tannin, which reduces the silver to the metallic condition and becomes converted into gallic acid with evolution of carbonic acid gas. It is best made up into pill with kaolin and a very little tragacanth. As a draught it may be made up with dilute nitric acid, syrup, and mucilage.