Enthalpy of dissolution and micellization in the sodium decyl sulfate-water system

The enthalpy of dissolution of sodium decyl sulfate (SDeS) in water was mea sured at 298 K in the region of true and micellar solutions (from 4.5 x 10( -4) to 15 x 10(-2) mol/l) using an isoperibolic calorimeter. The dissolutio n enthalpy isotherm has three maximums corresponding to the most essential changes in the structure of the solutions: the full hydration boundary for SDeS in true solutions, its first critical micellization concentration (CMC 1), and the intermediate micellar transition (CMC1-2). The energy of this t ransition was estimated. Results obtained for the region of high dilutions were discussed in terms of changes in the structure of the solvent in respo nse to the introduction of Na+ and DeS(-) ions. Proposals regarding the ene rgy and entropy contributions to the Gibbs energy of dissolution of SDeS in water were made.