Dissolve 7 parts of crystallized carbonate of soda, and 7 1/2 of tartaric acid, in 24 of boiling water; add to the boiling solution 6 parts of chlorate of potash in 16 of water, at 212° F., agitating the mixture. When quite cold filter, and add a solution of 6 parts of oxalic acid in 18 of water, heated not above 134° F. Agitate well, place the vessel in a freezing mixture of hydrochloric acid and sulphate of magnesia, and filter. [Not absolutely pure, but sufficiently so for technical purposes. It may be obtained pure by decomposing chlorate of baryta by sulphuric acid.] Acid, Chromic. It may be obtained pure by mixing bichromate of potash with nitrate of silver in solution, washing the precipitate, and decomposing it with an equivalent quantity of hydrochloric acid. In a few minutes the clear solution may be poured off. See Aciduin Chromicum, Pocket Formulary. Acid, Cinnamic. It is most readily procured by distilling genuine balsam of Tolu by a gentle heat. The white crystalline mass which condenses on the neck of the retort is purified by pressing it between blotting paper, dissolving in boiling water, and recrystallizing. Acid, Fluoric - Acid, Hydrofluoric. The anhydrous acid is made by distilling powdered fluor spar with twice its weight of oil of vitrei, in a leaden, or better, a silver alembic, the pipe of which fits into a bottle of the same material, surrounded with ice. But as it is usually required in a diluted state, water equal in weight to the spar, may be put into the receiver. Great care must be taken, as the acid, both in its gaseous and liquid form, is very destructive.

Acid, Hippuric Mix the urine of the horse with milk of lime, boil for some minutes, and strain. Boil down the clear liquid to 1/8 of its bulk, avoiding burning; add hydrochloric acid, press the impure acid, boil it with fresh milk of lime, and again precipitate with hydrochloric acid.