Adsorption de l'adenosine a l'electrode de mercure—II. Etudes thermodynamique et cinetique de la formation de la phase condensee aux densites de charges fortement negatives

Abstract

The adsorption of adenosine (Na 2SO 4, Cs 2SO 4 1 N electrolyte) at the mercury electrode reveals the existence of two capacity pits resulting from the formation of a condensed film at the low charge densities and the high negative charge densities. In the latter case, the thermodynamic data show that the pit divides two adsorption ranges which correspond respectively to a low or a high adsorption of the surfactant and where the superficial structures are different by the spatial arrangement of the molecules. The kinetics of formation of the condensed, studied by the potential step method, is controlled by a two dimensional nucleation and growth process. The rate of relaxation measured is a function of the initial potential situated respectively in the low adsorption range or in the high adsorption range. The asymmetrical kinetic behaviour can be explained by the difference between the metastable states prior to the relaxation depending on the initial potential.