Twenty grms. hydrochloric acid are poured over 10 grms. powdered uric acid, and to the mixture previously heated to 35°, 24 grms. finely powdered potassium chlorate are slowly added in small quantities at a time with constant stirring. When about four-fifths of the chlorate has been added, the uric acid has nearly dissolved, and the liquor has a faint yellow colour. It is diluted with double the volume of water, allowed to stand for about one hour and filtered. The filtrate is saturated with sulphuretted hydrogen, and yields, after being left for 12 hours, crystalline crusts, often of a reddish tint, of alloxantin mixed with sulphur. It is filtered and washed with cold water, and the alloxantin dissolved in a small quantity of hot water and filtered off from the residue of sulphur. On cooling the filtrate, colourless crystals separate out. CH4NO3 + 0 + H„O = С4H2N2O4 + CON,H Uric Acid Alloxan Urea. 2C4H2NO4 + H2S = C ̧H4NO3 + S + H2O Properties. Hard Alloxantin. colourless crystals, scarcely soluble in cold, more readily in hot water; gives with baryta water a characteristic violet precipitate. PREPARATION LXXXII. ALLOXAN, CH,N,O=CO/NH.CO (Mesoxalylurea.) NH.CO CO LITERATURE.-Liebig, Wöhler (1838), Ann. Ch. Pharm. 26, 256; Liebig (1868), Ann. Ch. Pharm. 147, 366; E. Fischer (1882), Ann. Ch. Pharm. 215, 310. 10 grms. alloxantin. IO 20 conc. nitric acid (sp. gr. 1°42). Ten grms. finely powdered alloxantin are added to a mixture of 20 grms. fuming nitric acid (sp. gr. 1.5), and 10 grms. conc. nitric acid (sp. gr. 1·42), and allowed to stand. Slight evolution of nitrous fumes occurs, and the alloxantin, which at first remains at the bottom of the vessel, slowly changes into the more bulky crystals of alloxan, which gradually fill the liquid. The reaction lasts about two days, and is complete when a sample dissolves readily and completely in cold water. The crystalline mass is spread upon a porous plate, thoroughly dried in the air, and freed from traces of nitric acid by heating in a basin on the water-bath until the smell of the acid disappears. Alloxan may be obtained in large crystals by dissolving the dry product in the smallest quantity of hot water and allowing the solution to evaporate slowly. Properties.-Colourless brilliant crystals, containing four molecules of water of crystallisation, very soluble in water. |