C5H4N4O3  +

H2O + 0 s C4H6N4O3 + CO2 . It has been synthesized by E . Grimaux by heating one part of glyoxylic acid with two parts of urea for ten hours at too° C.: 2CO(NH2)2+ CH(OH)2COOH= 3H20 + C4H6N4O3 . It forms glancing prisms of neutral reaction slightly soluble in water . On standing with concentrated potassium hydroxide solution it gives potassium allantoate C4H7N4O4K . On heating with water it undergoes hydrolysis into urea and allanturic acid CsH4O3N2 . It is reduced by sodium amalgam to glycouril C4H6N4O2, whilst with hydriodic acid it yields urea and hydantoin C3H4N2O2 . Hot concentrated sulphuric acid also decomposes allantoin, with production of ammonia, and carbon monoxide and dioxide . By dry distillation it gives ammonium cyanide .