GENERALIZED EXPRESSIONS FOR CHEMICAL-POTENTIALS AND ADSORPTION-ISOTHERMS OF NEUTRAL ORGANIC-COMPOUNDS ON ELECTRODE SURFACES

Generalized expressions for the chemical potentials of the constituent s of films absorbed on ideally polarized electrode surfaces and compos ed of neutral organic absorbates are derived within the frames of clas sical thermodynamics and the electrostatic theory of the dielectrics. The chemical potentials are used for the derivation of adsorption isot herms, the properties of which are compared with experiment. This comp arison reveals that the dipoles of the adsorbed species do not reorien tate continuously, but they have either a constant or certain distinct orientations with respect to the electrode surface. In this case, the isotherms are in general congruent with respect to the potential drop across the adsorbed film. Deviations from the congruence may reflect either the existence of more than one solvent state simultaneously at the adsorbed layer or changes in the thickness of this layer during th e adsorption process. The analysis of the adsorbed layer properties ha s not led to conditions which favour the appearance of congruence with respect to the electrode charge density.