Uric acid is commonly determined in biological fluids by measuring the blue colour produced by its reaction with reagents containing phosphotungstic or arsenotungstic acids under conditions which minimize interference by other reducing substances (Folin & Denis, 1912; Folin, 1933, 1934; Benedict, 1912, 1922; Brown, 1945; Bidmead, 1951). Recovery of uric acid added to blood has never been comple...