Acoustical Study and Thermodynamics of Dissociation and Micellization of Lanthanum and Cerium Linoleates in A Mixture of Benzene and Methanol

Abstract

Abstract Ultrasonic measurements on lanthanum and cerium linoleates were made in a mixture of 60% benzene and 40% methanol (V/V), to determine the CMC, soap-solvent interaction and various acoustic and thermodynamic parameters. The values of the CMC increase with the increase in temperature. The ultrasonic velocity, specific acoustic impedance, apparent molar compressibility, relative association and Rao's number increase while the adiabatic compressibility, intermolecular free length, apparent molar volume, solvation number and available volume decrease with increasing soap concentration. The dissociation constant and thermodynamic parameters for dissociation and micellization processes of lanthanum and cerium linoleates were evaluated from conductivity measurements. The results showed that these soaps behave as weak electrolytes in dilute solutions and the micellization process is dominant over the dissociation process.