HIPPU′RIC ACID

HC 9 H 8 NO 3 . Syn. Acidum hippuricum , L. A compound discovered by Liebig in the urine of the horse, cow, and other gram in i vor a, in which it exists as hippurate of pota ium or sodium. Prep. Concentrate fresh cow’s urine by a gentle heat to about 1 ⁄ 10 th its bulk, filter from deposit, mix the liquid with exce of hydrochloric acid, and set it aside to crystallise. It may be decoloured by redi olving it in boiling water, and treating it with animal charcoal, or with a little chloride of lime along with some hydrochloric acid, and re-crystallising it. Obs. Hippuric acid, when pure, forms long, slender, milk-white, square prisms; it is soluble in 400 parts of cold water; it also di olves in hot alcohol. When strongly heated, it yields benzoic acid, benzoate of ammonia, and benz on it rile, with a coaly residue. The urine of horses or cows, left to itself for some time, or evaporated at a boiling temperature, yields not a trace of hippuric acid, but only benzoic acid. Nitric acid and hot oil of vitriol convert it into benzoic acid. Boiling hydrochloric acid converts it into benzoic acid and glycocoll. With the bases it forms salts, which are called hippurates. See Benzoic Acid .