citric acid

citric acid or 2-hydroxy-1,2,3-propanetricarboxylic acid, HO ₂ CCH ₂ C(OH)(CO ₂ H)CH ₂ CO ₂ H, an organic carboxylic acid containing three carboxyl groups ; it is a solid at room temperature, melts at 153°C, and decomposes at higher temperatures. It is responsible for the tart taste of various fruits in which it occurs, e.g., lemons, limes, oranges, pineapples, and gooseberries. It can be extracted from the juice of citrus fruits by adding calcium oxide (lime) to form calcium citrate, an insoluble precipitate that can be collected by filtration; the citric acid can be recovered from its calcium salt by adding sulfuric acid. It is obtained also by fermentation of glucose with the aid of the mold Aspergillus niger and can be obtained synthetically from acetone or glycerol. Citric acid is used in soft drinks and in laxatives and cathartics. Its salts, the citrates, have many uses, e.g., ferric ammonium citrate is used in making blueprint paper. Sour salt, used in cooking, is citric acid.

citric acid (sit-rik) n. an organic acid found naturally in citrus fruits. Citric acid is formed in the first stage of the Krebs cycle. Formula: CH₂(COOH)C(OH)(COOH)CH₂COOH.

citric acid A white crystalline hydroxy carboxylic acid, HOOCCH₂C(OH)(COOH)CH₂COOH. It is present in citrus fruits and is an intermediate in the Krebs cycle in plant and animal cells.