The photochemical degradation kinetics of Sodium pamino-Phenyl Sulphonate in aqueous solution and CdS colloid systems was studied by means of ESR method, and the kinetics behaviour for both the photoreactions in aqueous solution system and in CdS colloid system was compared. The results indicated that both the initial concentrations of SSN and the presence of CdS colloid obviously affected the photodegradation processes of SSN in the way of enhancing the rate constants for the formation of free radical SO3. The kinetics processes of photoreartions were treated by the quasi-stationary analysis method, the results of analysis are consistent with the phenomena observed in our experiments. The experimental results were briefly analyzed and discussed.
