MALIC

ACID (HYDROXYETHYLENE SUCCINIC ACID), CIHSO5  , an organic acid found abundantly in the juices of many plants, particularly in mountain-ash berries, in unripe apples and in grapes . The acid potassium salt is also found in the leaves and stalks of rhubarb . Since the acid contains an asymmetric carbon atom, it can exist in three' forms, a dextro-rotatory, a laevo-rotatory and an inactive form; the acid obtained in the various synthetical processes is the inactive form . It may be prepared by heating racemic acid (see TARTARIC ACID) with fuming hydriodic acid; by heating fumaric acid (q.v.) with water at 150--200° C.; by the action of nitrous acid on inactive aspartic acid; and by the action of moist silver oxide on monobromsuccinic acid . It forms deliquescent crystals, which are readily soluble in alcohol and melt at loo° C . When heated for some time at 13o° C. it yields fumaric acid (q.v.), and on rapid heating at 18o° C. gives maleic anhydride and fumaric acid . It yields coumarins when warmed with sulphuric acid and phenols (H. v . Pechmann, Ber., 1884, 17, 929, 1649 et seq.) . Potassium bichromate oxidizes it to malonic acid; nitric acid oxidizes it to oxalic acid; and hydriodic acid reduces it to succinic acid . The inactive variety may be split into the component active forms by means of its cinchonine salt (G . J . W .

Bremer, Ber., 188o, 13, 352) .