Activity coefficients of alkyl sulfate and alkylsulfonate ions in aqueous and water-salt premicellar solutions

Potentiometry has been employed to determine the activity coefficients of n-decyl sulfate and n-alkyl(C₅–C₁₀)sulfonate ions in aqueous solutions of their sodium salts containing NaCl or Na₂SO₄ as a background electrolyte. The selectivity factors have been estimated for ion-selective electrodes exhibiting responses to surfactant ions in the presence of inorganic salts. The pattern of the dependences of the activity coefficients of the surfactant anions on the length of their hydrocarbon radicals and the nature of functional groups has been revealed. The results obtained have been compared with the data on long-chain carboxylates.