Model for the Conductivity of Ionic Mixtures in the Mean Spherical Approximation. 2. Surfactant Solutions

We recently obtained analytic expressions for the concentration dependence of the conductance of a mixture with three simple ionic species. These expressions are available at concentrations up to 1 equiv of solute per liter of solution. The success of our description is based on the use of the mean spherical approximation (MSA). It yields explicit formulas in terms of the MSA inverse screening length Γ and the dynamical Debye−Falkenhagen length. We present here results obtained for ionic surfactant systems where, above the critical micellar concentration (cmc), three charged species are present in the solution. From the accuracy of the results one may infer that the size and the charge of ionic micelles above the cmc could be determined using conductivity experiments.