Micelle Formation of Sodium 1-Decanesulfonate and Change of Micellization Temperature by Excess Counterion

Aqueous solution properties of sodium 1-decanesulfonate have been studied at 308.2 K by electroconductivity, membrane potential, and photochemistry in order to determine the micellization parameters for the mass-action model: the micellization constant K n, the micellar aggregation number n, and the number of counterions binding to a micelle m . The numerical values are ln K n = 133, n = 26, and m = 16.6. These values account for the experimental concentrations of the surfactant ion and counterion to a concentration that is 3 times the critical micelle concentration (cmc). The micellization temperature (MT) or the Krafft temperature was determined to be 295.3 K from the temperature dependence of the cmc and of the aqueous solubility. The MT values shifted to higher temperature with increasing concentration of sodium chloride, and good agreement was found in the values evaluated from the difference between the aqueous solubility and the cmc in the presence of excess counterion.