Citric Acid

Citric Acid, a tribasic acid of the composition C₆H₈0₇ which occurs largely in the juice of many fruits, as lemons, gooseberries, currants, etc. It is chiefly obtained from lemon or lime juice, in which it occurs to about 8 per cent., by addition of chalk, and treatment of the calcium citrate so obtained with the required quantity of sulphuric acid. It forms rhombic crystals easily soluble in water, and possesses a very sour taste. Its salts are termed citrates, and some are employed medicinally, as citrate of iron, citrate of iron and quinine, both well-known tonics. Citrate of magnesia consists chiefly of a mixture of tartaric acid, citric acid, and bicarbonate of soda, and contains but little magnesia. The acid and its salts are also used for photographic purposes.