ALLOXAN, a product of the action of oxidising agents on uric acid, obtained by adding slowly, in small quantities, uric acid to strong nitric acid of specific gravity 1 ∙ 4, kept cool, and stirring constantly. Carbonic acid and nitrogen are evolved during the action, and the alloxan crystallises out on standing. It is purified by recrystallisation from water, and then has the composition C 4 H 2 N 2 O 4 + aq. The crystals of this compound are large and colourless, and when heated to a temperature of 150° C., lose the water of crystallisation, and acquire a red colour. Alloxan is readily soluble in water and alcohol, and its aqueous solution reddens litmus, has an astringent taste, and colours the skin purple after some time. It produces a great number of derivatives, for which see Uric Acid.