AQUEOUS MICELLAR SOLUTIONS OF SODIUM DODECYL-SULFATE IN TETRAMETHYLAMMONIUM CHLORIDE

Electromotive force measurements of galvanic liquid junction free cells containing two glass electrodes, one reversible to sodium ions and the other reversible to hydrogen ions, were performed at 25-degrees-C on buffered solutions of sodium dodecyl sulfate (SDS) within the concentration range 0-0.1 M. The critical micellar concentration and the degree of association of sodium ions to the micelles were determined. It emerges that a SDS bilayer structure can explain the experimental data. Measurements were also carried out by using 0.50, 0.30 and 0.15 M N(CH3)4Cl as ionic medium. The results could be explained by assuming the presence of species of the type Na(q)(DS)n, where DS represents the dodecyl sulfate moiety and q and n are integer numbers. The q and n values increase by increasing the ionic medium concentration.