Electrochemical studies of micelle–counterion interactions in mixtures of ionic and non-ionic surfactants
- 1 January 1984
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 80 (5) , 1193-1199
- https://doi.org/10.1039/f19848001193
Abstract
For solutions containing a 1 : 1 ionic surfactant plus a 1 : 1 electrolyte with a common counterion the expression α2 ±=C3[C3+m1+α(C1–m1)]γ2 is used to estimate the effective micellar degree of dissociation α from experimental values of a±. The mean ionic activity of supporting electrolyte in situations where m1 C3 C1(C3, C1 and m1 denote concentrations of added salt, total ionic surfactant and ionic-surfactant monomer, respectively, and γ is an appropriate activity coefficient). The method is free from uncertainties due to liquid-junction effects. For pure ionic surfactants α is found to depend only weakly on C1 and agrees well with values obtained from the effect of salt on the c.m.c. For mixtures of ionic + non-ionic surfactants 1/α is found to vary linearly with micellar mole fraction of the non-ionic xN and aproach unity as xN→ 1. The implications of this finding on the validity of a recent theory describing the c.m.c. of such mixtures is discussed.Keywords
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