Volumes molaires partiels de composés tensioactifs dans les milieux salins concentrés eau–KCl

Abstract

Apparent molar volumes of 4 cationic detergents CH3(CH2)nN(CH3)3Br (n = 9, 11, 13, and 15) have been determined in water – potassium chloride mixtures at 298 K over a wide range of concentrations (from 0.5 to 3.5 mol L−1). The small dependence of values of apparent molar volume of micellized detergent on the salt concentration suggests the interactions between amphiphiles themselves and between amphiphiles and their surroundings are not modified by the variation of KCl concentration. Previous results lead to estimates of intrinsic volumes of micellized detergents and consequently actual volumes of the micellar phase in the solution. In addition, apparent molar volumes of dodecyltrimethylammonium bromide and sodium dodecylsulfate have been determined in water – sodium chloride mixtures. The results agree fairly well with the previous conclusions and prove the dissymmetric behaviour of the anions and cations in very highly concentrated aqueous salt solutions.