Hydrodynamic Potentiometry and Amperometry at Ring-Disk Electrodes

An electronically regulated speed control unit has been programmed to produce an w1/2 = Kt relation for disk and ring-disk electrodes. Besides automatic hydrodynamic amperometry (Levich plots), one can perform two new techniques of hydrodynamic potentiometry: (a) recording of disk potential (ED) vs. w1/2 at constant disk current (in); and (b) recording of Ed vs. Id at constant surface concentrations of all species, obtained by holding Id/w1/2 constant while scanning iD. The equations governing (a) are derived and the implications of (b) for measuring rate constants and/or uncompensated solution resistance are discussed.