The specific conductivities of dodecyldimethylethylammonium bromide (C12DEABr) have been determined in aqueous-butanol solutions in the temperature range of 15-40 degreesC. From these data the temperature dependent critical micelle concentration (cmc) was determined. The molar fraction of alcohol in the micelle was estimated using the theory suggested by Motomura et al. [Colloid Polym. Sci. 262 (1984) 948] for surfactant binary mixtures. The standard Gibbs free energy of solubilization of alcohols in the micelles was estimated for the phase separation model, and the results were discussed in comparison with the corresponding alkyltrimethylammonium bromide. (C) 2004 Elsevier B.V. All rights reserved.