Summary Phenylglyoxal reacts with urea in cold basic solution to form 4-phenylhydantoin, and, when refluxed in basic solution to form on cooling and acidifying 2-ket0-4-phenyl-4~ 5- dihydroxytetrahy-droglyoxaline which on melting loses water to become 4-phenylhyda~ itoin. Phenylglyoxal and urea rcfluxrd it1 glacial