LINKS BETWEEN BULK AND SURFACE-ACTIVITY IN MICELLAR SOLUTIONS

The surface tension of aqueous surfactant systems and its dependence on the concentration of surfactant in micellar form, X(m) is-approximately-equal-to X- CMC, have been investigated. A modification of the adsorption equation, based on the introduction of activity coefficients, allows to get information on micelle aggregation numbers, [N], from the slope of surface tension versus ln X(m). The resulting equation, tested on data relative to non ionic surfactants, gives aggregation values in fair good agreement with those inferred from other methods. The limits of the model are discussed in some detail.