tartaric acid

tartaric acid HO ₂ CCHOHCHOHCO ₂ H, white crystalline dicarboxylic acid. It occurs as three distinct isomers , the dextro-, levo-, and meso- forms. The dextro- and levo- forms are optically active; the meso- form is optically inactive, as is racemic acid, a mixture of equal parts of the dextro- and levo- forms. Tartaric acid is found in many plants, e.g., grapes; this natural acid is chiefly the dextrorotatory d -tartaric acid, called also d -2,3-dihydroxysuccinic acid or l -2,3-dihydroxybutanedioic acid. This form can be partially converted to the others by heating it with an aqueous alkali, e.g., potassium hydroxide. Tartaric acids can be synthesized from maleic acids or fumaric acids by reaction with aqueous potassium permanganate. The various isomeric forms differ in such physical properties as boiling point. Tartaric acid is used chiefly in the form of its salts, e.g., cream of tartar and Rochelle salt .

tartaric acid A dibasic acid, chemically dihydroxysuccinic acid. Occurs in fruits, the chief source being grapes; used in preparing lemonade, added to jams when the fruit is not sufficiently acidic (citric acid also used) and in baking powder. Rochelle salt is potassium sodium tartrate. See also cream of tartar.

tar·tar·ic ac·id • n. Chem. a crystalline organic acid, COOH(CHOH)₂COOH, that is present esp. in unripe grapes and is used in baking powders and as a food additive.