Partial molal volumes and compressibilities of n-alkanes in aqueous solution of sodium-octanoate and sodium-decanoate

Abstract

Partial molal volumes and compressibilities have been determined for n-alkanes (C 7C 10) in aqueous solution of sodium-octanoate and sodium-decanoate at 25°C. These quantities have also been determined for the pure liquid alkanes. The partial molal volumes and compressibilities were determined by density measurements and ultrasound measurements, respectively. The partial molal volumes and compressibilities of the alkanes in the surfactant solutions are higher than those in water, especially the compressibilities, and resemble the partial molal quantities of the liquid alkanes. The partial molal volumes are almost independent of the chain length and the concentration of the surfactant. The partial molal compressibilities decrease slightly with decreasing chain length of the surfactant and with increasing micellar concentrations. These results have been interpreted from differences in the hydration and the structure of the micelles.