The effect of a background electrolyte on the premicellar association and average activity of sodium dodecyl sulfate ions

摘要

Premicellar association in a sodium dodecyl sulfate-NaCl-water system is studied by potentiometry using a sodium-selective electrode. The dependences of constants and degrees of dimerization of surfactant molecules on the background electrolyte concentration are determined. The average activity coefficient of surfactant ions is shown to increase with the ionic strength of a solution. The disclosed regularity is explained in terms of the Debye-Huckel theory with allowance made for the dependence of premicellar solution composition on the content of NaCl.