A study of superficial associations at a mercury electrode in the case of tetrabutylammonium halide solutions

The influence of the nature of the anion on the adsorption of the tetrabutylammonium cation from halide solutions at a mercury—solution interface has been studied. A series of measurements of the interfacial tension for such solutions also containing a non-adsorbable cation, have led to the evaluation of the adsorption of both the tetraalkylammonium cation and of the halide anion. The variation of global surface excesses of entropy and concentration with temperature have also been determined. The results obtained can be explained by the formation, at the surface of the electrode, of both paired and non-paired ions, the latter neutralizing the charge on the electrode. The role of hydrophobic forces whose importance has been recognized in the adsorption of neutral substances is stressed in the case of surfaceactive cations.