Cationic surfactants in organic solvents. II. Viscosity and conductance of trilaurylammonium salts in carbon tetrachloride and benzene

Abstract

The viscosity and conductance of carbon tetrachloride and benzene solutions of trilaurylammonium chloride, bromide, nitrate, perchlorate, and tetrachloroferrate have been measured at 25°, 30°, and 35°C in the concentration range up to 0.15 or 0.2 molar. In some plots representing the physical property as a function of concentration a break is discernible which is usually attributed to the apparent critical micelle concentration. A comparison of the present results with vapor pressure lowering data on the same systems expressed in terms of aggregate-size distribution curves, reveals that the apparent cmc is associated with the formation of higher oligomers in dynamic equilibrium with monomeric and dimeric (or trimeric) species. The apparent heats of micellization estimated from the viscosity data at different temperatures, suggest that the enthalpy changes are those of the desruption of single dipole-dipole bonds. The data support the mass-action law model of aggregation of surfactants in organic media.