Thermodynamic and aggregation properties of sodium n-hexylsulfonate (C6H13SO3Na) in aqueous solu-tions have been studied at different temperatures by density, sound velocity, electroconductivity andvapor–liquid equilibria measurements. The critical micelle concentration (CMC), counterion binding ofmicelles and thermodynamics of micellization have been evaluated. From the density and sound velocitydata, the values of the apparent molar volumes and compressibilities, changes in the apparent molarproperties upon micellization and the infinite dilution apparent molar properties of the monomer stateof C6H13SO3Na in the aqueous solutions were determined. Vapor–liquid equilibrium data such as wateractivity, vapor pressure, osmotic coefficient, activity coefficient and Gibbs free energies were obtainedthrough the isopiestic method. A comparison between the mentioned thermodynamic and aggrega-tion properties of C6H13SO3Na in aqueous solutions with those of some other sodium n-alkylsulfonateswere also made and from which the effect of the alkyl chain length of the surfactant on the aggregationparameters were examined.
