The literature concerning specific surface energies of solids and the thermodynamics of solid electrodes is critically reviewed. It is pointed out that assumptions resulting in superficial energy and surface stress (S. Trasatti and R. Parsons, Pure Appl. Chem., 58 (1986) 451) being independent contributions to a general specific surface energy do not correspond to complete equilibrium with constant chemical potentials of the components throughout the system. An irreversible, usually time-dependent part of the specific surface energy is due to differences in the chemical potentials of the components in the interphase and in the bulk of a solid. Consequences of the irreversible part for the charge number of adsorbed species and the frequency dependence of the double-layer capacitance are outlined.