Partial molar volumes of surface-active agents in aqueous solution

Abstract

The partial molar volumes V₂ of some ionic and non-ionic surface-active agents have been determined above and below the critical micelle concentrations. The change ΔV₂ in partial molar volumes on micelle formation is determined by molecular structure. Thus, additional methylene groups in the alkyl chain remote from the hydrophilic group give an increase in ΔV₂, while additional methylene groups in close proximity to a hydrophilic centre give a small decrease in ΔV₂. These results indicate that in the process of micelle formation the hydration of the methylene groups adjacent to the hydrophilic group is retained.