MASS-ACTION MODEL OF MICELLE FORMATION - ITS APPLICATION TO SODIUM DODECYL-SULFATE SOLUTION

The mass action model was applied to micelle formation of an ionic surfactant in aqueous solution. A method was developed to evaluate the micellization constant, the micelle aggregation number, and the number of counterions per micelle from the bulk concentrations of surfactant ion and/or counterion at definite surfactant concentrations, where the monodispersity of micelles was assumed. Application of the method to the micellization of sodium dodecyl sulfate demonstrated excellent agreement between the calculated and the reported values of the bulk concentrations from the CMC up to a concentration of 10 times the CMC. The slope of the logarithm of CMC against the logarithm of total counterion concentration turned out to be approximately equal to the degree of counterion association with the micelle.