ELECTRODE-SKIN IMPEDANCE FROM A DIELECTRIC VIEWPOINT

It is well established that the frequency variation of the complex ele ctrode-skin impedance (ESI) (Z) over cap is given by (Z) over cap = K( i omega)(-n), where n has a typical value of about 0.8. It is not easy to find a physical reason for this behaviour. However, many materials exhibit Cole-Davidson (CD) behaviour, so that in the high-frequency ( hf) region their impedance has a characteristic which is almost indist inguishable from that of the ESI. It is therefore possible that the ES I exhibits a behaviour given by the CD equation or one of its variants , but that this has not been detected because experimental measurement s have not extended to sufficiently low frequencies. Whatever the ESI behaviour may be at low frequencies, there are theoretical reasons whi ch show that (Z) over cap cannot obey the above equation indefinitely as the frequency is reduced. If the deviation from it at low frequenci es were found to be consistent with CD behaviour, then a physical expl anation in terms of protonic fluctuations, which has previously been p ut forward to explain CD behaviour, would be available as a possible e xplanation of ESI behaviour over the whole frequency range. It is show n that any such deviation would be more likely to be detected if the v ariation of complex capacitance with frequency, rather than of impedan ce with frequency, were to be plotted.