Generalized expressions for the chemical potentials of the constituents of films absorbed on ideally polarized electrode surfaces and composed of neutral organic absorbates are derived within the frames of classical thermodynamics and the electrostatic theory of the dielectrics. The chemical potentials are used for the derivation of adsorption isotherms, the properties of which are compared with experiment. This comparison reveals that the dipoles of the adsorbed species do not reorientate 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 the adsorption process. The analysis of the adsorbed layer properties has not led to conditions which favour the appearance of congruence with respect to the electrode charge density.