Uric Acid

Collier's New Encyclopedia (1921)

a very important excrementitious product, which occurs in small quantities in human urine, to the extent of rather less than 1 per cent. of the solid matter contained in it. It is met with in much greater abundance in the excrement of birds and reptiles, that of the boa consisting almost entirely of urate of ammonia. Guano also contains large quantities of it, and has been most extensively employed as its source in the of almost extinct manufacture now murexide dyes. When excess of uric acid is secreted in the system, it deposits hard crystallizing grains in the bladder, which, if retained, gradually form concretionary calculi, and grow into the disease known as gravel or stones. In gouty patients, uric acid accumulates around the joints, forming white friable concretions, known improperly as chalkstones. Uric acid is generally prepared by dissolving the dried excrement of the boa in water, and converting the urate of ammonia into nitrate of potash by adding excess of potash, and boiling till the whole of the ammonia has been set free. Hydrochloric acid is then added, and the acid separates in minute crystals, which are thoroughly washed and dried. Pure uric acid is a white crystalline powder, requiring 10,000 parts of water for solution, to which it imparts a very feeble acid reaction. It is insoluble in alcohol and ether, but dissolves in concentrated sulphuric acid, which deposits it in a hydrated condition or dilution. The urates of the alkalies are much more soluble than the acid itself. Uric acid is dibasic, giving rise to acid and neutral salts. By By being submitted to heat, uric acid breaks up into a number of compounds, but the remarkable number of definite and crystallizable substances which it gives rise to, when treated with various oxidizing agents, present the highest physiological interest, inasmuch as the great changes which occur in the animal economy under the influence of vitality are always accompanied by oxidation.