GUANIN, A yellowish white amorphous substance, which derives its name from its being a constituent of guano. It also forms, however, the chief constituent of the excrement of spiders, has been found attached to the scales of fishes, and seems to be a normal constituent of the mammalian liver and pan creas.
With regard to its occurrence in guano, as it has not been found in the recent excrement of sea-birds, there is every reason to believe that it is formed by slow oxidation (from atmospheric action) of uric acid, much as uric acid can be made to yield urea and oxalic acid. In the pan creas and liver it probably represents one of those transitory stages of disintegrated nitro genous tissues which are finally excreted by the kidneys in the more highly oxidized form of urea.
Guanin may be best prepared from Peruvian guano, which is for this purpose finely powdered and boiled with lime until the filtrate becothes colorless; the residue is then boiled with sodium carbonate solution, the liquid is filtered and precipitated with acetic acid. To purify the
guanin thus obtained, it is boiled with dilute hydrochloric acid, from which it is subsequently freed by the use of concentrated ammonia. Gua nin is insoluble in water, ether, alcohol, and am monia. By the action of oxidizing agents it is converted into guanidin, parabanic acid, and carbon dioxide. The presence of guanin may be analytically detected with the aid of concentrated solutions of potassium chromate and potassium ferrocyanide, the former reagent producing an orange-colored, the latter a yellowish-brown, crys talline precipitate, in solutions of guanin. When treated with nitrous acid, guanin is transformed into xanthin. The chemical constitution of gua nin has been determined by Emil Fischer.