The azo coupling reaction between diazotized 2-naphthylamine-3, 6, 8-t
risulphonic acid and S-aminophenylurea was studied. The reaction proce
eds together with decomposition of the diazonium salt. The rate consta
nts of both reactions were estimated potentiometrically. A theoretical
relationship of the azo coupling reaction product and time was calcul
ated, and compared with the experimentally observed data.