THERMODYNAMIC AND AGGREGATION BEHAVIOR OF MIXED MICELLAR SYSTEMS OF SODIUM DECANOATE AND ETHOXYLATED ALCOHOLS IN WATER AT 25-DEGREES-C

Densities and ultrasonic velocities of binary aqueous systems of sodiu m decanoate (C10Na), of a medium chain length alkoxyethanol with varyi ng number of ethylene oxide groups (C4EO0-3), and of ternary systems o f these compounds have been measured as a function of surfactant and a lcohol concentrations at 25 degrees C. The derived apparent molar volu me and molar adiabatic compressibility properties of C10Na in water we re fitted with a mass-action model to obtain the thermodynamic micelli zation parameters of C10Na. The infinite dilution transfer molar volum e and transfer molar adiabatic compressibility properties of C4EO0-3 f rom water to aqueous C10Na solutions were obtained from the correspond ing apparent molar properties using a chemical equilibrium model. The results of simulating the experimental transfer function data of these alcohols at a given low concentration of 0.05m(A) show that the solub ilization of C4EO0-3 compounds in C10Na micelles is enhanced by increa sing the number of ethylene oxide groups (EO) in the alcohol. The mean aggregation number of C10Na, which is 34 in the absence of alcohol, r emains unchanged in the presence of 0.05m(A) while the average number of alcohol molecules per micelle increases steadily as a function of t he number of EO groups in the alcohol.