Malic Acid, H_2C_4H_5O_5

Malic Acid, $H\_2C\_4H\_5O\_5$ (from Lat. malum, 'an apple'), occurs abundantly in most acidulous fruits, particularly in unripe apples, gooseberries, and currants, in which it is found as an acid or acid salt of potash or lime, which gradually changes into a neutral salt as the fruit ripens. It crystallises in groups of radiating acicular prisms, but, as the crystals are very deliquescent, it is usually obtained as a syrupy, semi-transparent mass, with a very sour smell, and readily soluble in water and alcohol. The chemical changes which this acid undergoes under the influence of various reagents are very singular, and serve to illustrate many points in vegetable physiology in reference to the maturation of fruits. Thus, nitric acid converts it into oxalic acid; hydrated potash, into oxalic and acetic acids; ferments, into succinic, butyric, acetic, and carbonic acids and water.