How to check the validity of Nernst's law in a potentiometric solid electrolyte galvanic cell

To answer the question as to whether Nernst's law holds and to what extent an electron transference occurs in a potentiometric cell, four criteria are discussed on the basis of practically relevant instances: (i) the total vo ltage, (ii) the chemical potential dependence of the voltage, (iii) the tem perature dependence of the voltage and (iv) the chemical potential dependen ce of the temperature coefficient of the voltage. In view of recent finding s on the peculiar property of the electron conduction parameters according to which these parameters may change with the chemical potential in the sur rounding of the electrolyte, the agreement between the experimental and the Nernst value of the voltage may not longer be regarded a sufficient prereq uisite for the validity of Nernst's law. Under such a circumstance useful i nformation can particularly be derived from the criteria (ii)-(iv) which to date have received only limited attention. As a result, the present approa ch proves to be capable of quantitatively determining the deviation from th e Nern.st voltage without knowing the extent of the electron transference a nd the Nernst voltage itself. Further evidence for the sodium potential dep endence of the p-electron conduction parameter of Na-beta-alumina is given. (C) 1998 Published by Elsevier Science B.V. All rights reserved.