An Investigation Into The Enthalpy Change of Sodium Dodecyl Sulphonate Micelle Formation

The critical micelle concentrations of sodium normal dodecyl sulphonate have been measured by conductivity measurement at temperatures of 313.2K, 318.2K, 323.2K and 328.2K. The dissociation degrees of the surfactant in the micelle at various temperatures have been calculated. The equation of the enthalpy change of ionic surfactant micelle formation was modified as ΔH_m⁰=-\mathrmRT \frac\partial \ln \left(C M C)^(2-a)\right.\partial T in consideration of the variation of dissociation degree with temperature. The value of ΔH_m⁰ of sodium normal dodecyl sulpbonate at 313.2K was calculated as -6.96KJ/mol. and measured as -6.90KJ/mol. with a conductive calorimeter according to the dilution method. The result indicated that the modified equation could give a more consistent prediction with experiment than the original one.