ANTIMON′IC ACID

Syn. Acidum antimon′icum , L.; Acide an tim on i que , Fr.; An timonsäure , Ger. Prep. 1. Pure metallic antimony, in coarse powder, or small fragments, is digested in exce of concentrated nitric acid, until the oxidation and conversion is complete; the exce of nitric acid is then removed by evaporation nearly to dryne , and the residuum thrown into cold distilled water; after which the powder ( ANTIMONIC ACID ) is collected on a calico filter, washed with distilled water, and dried by a gentle heat. Pure. 2. Metallic antimony (in powder), 1 part; powdered nitre, 6 or 8 parts; are mixed and ignited or deflagrated in a silver crucible; the ma , when cold, is powdered; the exce of alkali washed out with hot water, and the residuum ( ANTIMONIATE OF POTASSIUM ) decomposed with hydrochloric acid; lastly, the precipitate ( ANTIMONIC ACID ) is washed and dried as before. That obtained by the first proce is dibasic, and has the formula and has the formula H 4 Sb 2 O 7 ; the former is called simply antimonic acid, the latter met antimonic acid. Prop. Antimonic acid is a soft white powder, sparingly soluble in water, reddens litmus, and is di olved, even in the cold, by strong hydrochloric acid and by potash. The hydrochloric solution, mixed with a small quantity of water, yields, after a while, a precipitate of antimonic acid; but if diluted with a large quantity of water, it remains clear. Ammonia does not di olve it in the cold. By heating with a large exce of caustic potash it is converted into met antimonic acid. Met antimonic acid is more readily di olved by acids than antimonic acid, and is di olved by ammonia, after a while, even at ordinary temperatures. It is also perfectly soluble in a large quantity of water, and is precipitated therefrom by acids. It is very unstable, and easily changes into antimonic acid, even in water.