A crystalline acid prepared from the acid tartrate of potassium.

Characters. - In colourless crystals, the primary form of which is the oblique rhombic prism. It has a strongly acid taste, and is readily soluble in water and in rectified spirit. When to either solution, not too much diluted, a little acetate of potassium is added, a white crystalline precipitate is formed.

20 grains neutralise

27 grains bicarbonate of potassium. 22 ,, „ sodium.

15 1/2 ,, carbonate of ammonium.

Preparation. - Vide p. 566.

Impurities. - Lead, copper, and iron from the vessels in which it is prepared; calcium, or acid tartrate of potassium, from the substances used in its preparation; racemic and oxalic acids.

Tests. - An aqueous solution of the acid is not affected by sulphuretted hydrogen (absence of metals), and gives no precipitate with the solution of sulphate of calcium (no racemic or oxalic acids), or of oxalate of ammonium (no calcium). It leaves no residue, or only a mere trace, when burned with free access of air (no acid tartrate of potassium).

Dose. - 10 to 30 grains.

Action and Uses. - Used for cooling drinks.