THE ABSOLUTE ELECTRODE POTENTIAL - AN EXPLANATORY NOTE (RECOMMENDATIONS 1986)

The document begins with the illustration of the most widespread misunderstandings in the literature about the physical meaning of absolute electrode potential. The correct expression for this quantity is then derived by a thermodynamic analysis of the components of the emf of an electrochemical cell. It is shown that in principle three reference levels can be chosen to measure an absolute value of the electrode potential. Only one of these possesses all the requisites for a meaningful comparison on a common energy scale between electrochemical and physical parameters. Such a comparison is the main problem for which the adoption of a correct scale for absolute electrode potentials is a prerequisites. The document ends with the recommendation of a critically evaluated value for the absolute potential of the standard hydrogen electrode in water and in a few other protic solvents.