Micellization behaviour of lithium dodecyl sulphate in aqueous solutions using conductivity, density and adiabatic compressibility measurements

Abstract

Temperature effects on micellar behaviour of lithium dodecyl sulphate in aqueous solutions have been measured using conductometric, densiometric, and interferrometric techniques. All these methods yield almost identical critical micelle concentration (cmc) for the surfactant system. Conductivity studies, in the range 288.15-318.15 K at 5 K intervals, show a shallow minimum of the cmc values at around 298.42 K. The ionization degree of micelles (α), has been round to increase whereas the standard free energy of micellization (ΔG_o^ɩɩɩ) decreases upon increase in temperature. Variation in standard enthalpy upon aggregation has been calculated by using Gibbs-Helmholtz equation. From density measurements carried out at 288.15, 298.15 and 308.15 K. the changes of the apparent molar volume upon micellization of the surfactant have been calculated. The apparent adiabatic compressibilities of the surfactant solutions have also been calculated using density and ultrasound velocity measurements and provide information on the solution behaviour of the surfactant in aqueous solution.