C5H4N403 URIC

ACID  , in organic chemistry, an acid which is one of the penultimate products of the tissue waste in the human body . While the bulk of the nitrogen of the albuminoids passes off through the bladder as urea, a small portion of it stops at the uric acid stage . Human urine contains only a fraction of a per cent. of the acid, chiefly as sodium salt; abundance of uric acid is met with in the excrement of serpents and birds, with whom it is the principal nitrogenous product of tissue waste . For its preparation guano is boiled repeatedly with a solution of borax in 120 parts of water . The filtered solution is acidified with hydrochloric acid, when impure uric acid separates out as a brown precipitate, which is washed with cold water; it is then dissolved in hot dilute caustic potash• or soda, the solution filtered, and the filtrate saturated with carbon dioxide . An almost insoluble urate is precipitated, which is filtered, washed and decomposed by hot dilute hydrochloric acid . Uric acid separates as a white precipitate, which is filtered off, washed and dried, to be repurified by a repetition of the alkali process or otherwise . Pure uric acid forms a snow-white micro-crystalline powder, devoid of smell or taste, soluble in 'Soo parts of boiling and in 14,000 parts of cold water, but in-soluble in alcohol and in ether . For its detection in urine, the urine is mixed with excess of hydrochloric acid, and allowed to stand, when the uric acid separates out, generally coloured reddish by impurities . The precipitate is dissolved in a few drops of nitric acid and the solution cautiously evaporated to dryness . The residue when exposed to ammonia gas assumes the intense purple colour of murexide . The acid, which was discovered by C .

Scheele in 1776 in urinary calculi, was afterwards investigated by Liebig and Wohler . The determination of its constitution, and its relation to other vegetable and animal products, followed from the researches of A. von Baeyer and E . Fischer (see PURIN) .