Defined for species B in phase β as \[\alpha _{\text{B}}^{\beta } = \mu _{\text{B}}^{\beta }\,-\,z_{\text{B}}\ F\ \psi ^{\beta }\] where \(\mu _{\text{B}}^{\beta }\) is the @E01945@ of species B in phase β, \(z_{\text{B}}\) is the @C00993@ of species B, \(F\) is the @F02325@, and \(\psi ^{\beta }\) is the @O04349@ of phase β. Since \(\psi ^{\beta }\) is zero when the charge on the phase β is zero, the real potential may be regarded as the value of the @E01945@ of the uncharged phase.