Prepn: H. W. Elley, H. W. Daudt, US 2224904 (1940 to Du Pont). Metabolism: J. L. Radomski, J. Pharmacol. Exp. Ther. 134, 100 (1961); 136, 378 (1962). Toxicology: M. Sharratt et al., Food Cosmet. Toxicol. 4, 493 (1966). Review of carcinogenicity studies: IARC Monographs 8, 101-106. See also Colour Index vol. 4 (3rd ed., 1971) p 4033.