A computational algorithm based on the Gauss-Newton iteration technique was developed to determine the composition of the mixed micelles of TritonX-100/SDS, the interaction between the two surfactants, β,and the activity coefficients of the surfactants in the micelle. Negative β values at different mole fractions of TritonX-100 were obtained which indicate synergism between the two surfactants. The catalytic effect of mixed micelles of TritonX-100/SDS on the hydrolysis of [Fe(tpy)2]2+in the presence of base was studied over a number of mole fractions (αa) of TritonX-100 and total surfactant concentrations(Ct). It was found thatthe rate of the reaction increases with αa and decreases with increasing surfactant concentration, Ct. The analysis of kinetic data was carried out by applying the pseudo phase model. Binding constants, KA, obtained from the kinetic data also indicate synergism between the two surfactants.