RATIONAL POTENTIAL

"The potential of an electrode expressed against the potential of zero charge (pzc) of the same electrode in the same solution. This provides a potential scale specific for each electrode, with the origin (zero potential) always at the respective pzc. Consequently, two electrodes having the same ""rational potential"" are typically not at the same ""potential"" (as measured against any reference electrode). However, the potential of these two electrodes is displaced by the same amount from their respective pzc; therefore, the charge density in the double layer of the two electrodes will be approximately equal. Consequently, the comparison of electrode behavior at the same ""rational potential"" is more meaningful for some purposes than a comparison at the same ""potential on some arbitrary scale."" The charge densities of two electrodes at the same rational potential are only approximately equal because the double-layer capacitance and its potential dependence varies from electrode to electrode. "