VEGETABLE acids, in chemistry. The acids which exist in many vegetables are at once recognized by their taste. These acids were fOrmerly denominated essen. tial salts of vegetables, and it was sup posed, that all essential salts were the same, and were composed of tartar, or vinegar. But Scheele 's discovery of the citric, malic, and gallic acids, which pos sessing distinct properties from those of tartaric and acetic acids, proved the con trary. Some vegetables contain only one acid, as oranges and lemons, which con. tam citric acid only. In other vegetables two acids are found, as in gooseberries and currants, the malic and citric acids ; and sometimes three, as the tartric, citric, and malic acids, which exist together in the pulp of the tamarind. As the acids which exist in vegetables have been al ready described, under their respective heads, it is now only necessary to enume rate the vegetable acids, specifying at the same time some of the plants from which they are obtained.
Acetic acid has been discovered in the sap of some trees, and in the acid juice of ricer arictinum. .. Oxalic acid exists in combination with potash, in the leaves of the oxalis acetosella, or wood-sorrel. In other species belonging to the same ge nus, and in some species 011'UlDe X, it is in the state of accidulous oxalate of pot ash. Oxalate. of lime has been found in the root of rhubarb.
Malic acid exists unmixed with other acids, in the apple, the barberry, plum, sloe, elder, &c In the gooseberry, in the cherry, strawberry, currants, and some other fruits, malic and citric acids are found nearly in equal proportions. Malic acid has been found mixed with tartaric acid in the agave Americana, and in the pulp of tamarinds, along with citric acid. Vauquelin found it combined with lime, flaming a malate of lime, in the semper virus tectorum, or house-leek. Gallic acid is found in a great number of plants and in them it exists chiefly in the hark. Benzoic acid is kund in benzoin, balsam of Tolu and Peru, liquid styrax, cinna mon, and vanilla. Fourcroy and Van quelin suspect that it exists in the anthox anthum odoratum, or sweet-scented grass, which communicates the aroma tic flavour to hay. Prussic acid has been found hi the leaves of the lauro-cerasus and peach, in bitter almonds, in the ker nels of apricots; and it is supposed that it exists also in the ker•els of peaches, of • plums, and cherries. It is obtained from the kernels of apricots, by distilling wa-, ter off them with a moderate heat ; and if lime be added to the concentrated infusion of bitter almonds, a prussiate of lime is formed. Phosphoric acid has been found in different parts of plimts ; but it is gene. rally combined with lime, forming
phase of lime.