Model for thermodynamics of ionic surfactant solutions. 1. Osmotic and activity coefficients

Equations have been derived for activity coefficients and osmotic coefficients of aqueous ionic surfactant solutions. The equations are based on a mass-action model with a single micellar aggregate species. The micellar solution is treated as a mixed electrolyte by using the Guggenheim equations. A shielding factor is included to account for screening of the micellar charge. The equations have been applied to experimental data for aqueous solutions of ionic surfactants. Osmotic and activity coefficient data from 0 to 50/sup 0/c and from 0.001 to 4 mol kg/sup -1/ have been correlated with the equations using a maximum of two ion-ion interaction parameters. Data for several surfactants have been described up to 1 mol kg/sup -1/ using no ion-ion interaction parameters. 50 references, 7 figures, 3 tables.