real potential of a species in a phase

Defined for species B in phase β as
α B β = μ B β − z B F ψ β
where μ B β is the electrochemical potential of species B in phase β, z B is the charge number of species B, F is the Faraday constant, and ψ β is the outer electric potential of phase β. Since ψ β is zero when the charge on the phase β is zero, the real potential may be regarded as the value of the electrochemical potential of the uncharged phase.
PAC, 1974, 37, 499 (Electrochemical nomenclature) on page 506