Prep. 1. Pure metallic antimony, in coarse powder, or small fragments, is digested in excess of concentrated nitric acid, until the oxidation and conversion is complete; the excess of nitric acid is then removed by evaporation nearly to dryness, 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 mass, when cold, is powdered; the excess 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 process is dibasic, and has the formula H2Sb2O6, while that produced by the second process is tetrabasic, and has the formula H4Sb2O7; the former is called simply antimonic acid, the latter metantimonic acid.
Prop. Antimonic acid is a soft white powder, sparingly soluble in water, reddens litmus, and is dissolved, 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 dissolve it in the cold. By heating with a large excess of caustic potash it is converted into metantimonic acid.
Metantimonic acid is more readily dissolved by acids than antimonic acid, and is dissolved 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.
ANTIMONIC ANHYDRIDE (Sb2O5). Syn. Antimonic Oxide, Anhydrous Antimonic Acid, Pentoxide of Antimony. Antimonic or metantimonic acid, heated to a temperature below redness, loses water and yields the anhydride, Sb2O5. Antimonic anhydride is a yellowish-white powder, tasteless and insoluble in water and acids. Boiled with a solution of caustic potash, it is dissolved. If fused with carbonate of potassium, carbonic anhydride is expelled, and a salt is produced from which antimonic acid is precipitated by acids.
ANTIMONIOUS ACID. See Antimony, Tetroxide of.
AN′TIMONETTED. Syn. Antimo′′niuretted; Antimonia′tus, L. Combined with or containing antimony. See Hydrogen,
&c.