Note:  Do not rely on this information. It is very old.

Creamof Tartar

Cream of Tartar. During the fermentation of grape juice for the production of wine, crystalline crusts are deposited on the casks, consisting chiefly of acid potassium, tartrate (H5KC4O6), and known as argol. By dissolving this in hot water, filtering with charcoal, clay, or albumen, and then allowing the liquid to crystallise, cream of tartar is obtained. It is generally, however, impure, containing small quantities of calcium tartrate. It forms rhombic crystals, and is only slightly soluble in cold water. Hot water, however, dissolves it more readily; and an intimate mixture with borax is easily soluble in the cold, and is known as soluble cream of tartar. It finds various industrial uses, as in manufacture of potassium carbonate, in silvering, dyeing, etc., and in medicine. In small doses it is used as a diuretic, while taken in larger quantities it acts as an aperient and purgative.