The Absolute Electrode Potential: Tying the Loose Ends

Abstract

A critical analysis is presented, concerning the phenomena which impact on the definition and concept of the absolute single electrode potential. These phenomena include the establishment of electronic equilibria across interfaces, the relevance of “free” electrons, the effects of liquid junctions, and the measurability, in vacuum, of both Volta potentials and work functions involving liquid solutions. The respective absolute potentials defined by Trasatti and Kanevski are confirmed, but the latter is subject to the serious limitation that it cannot be used to “construct” the potentials of full cells containing liquid junctions even when the junction potential has been “eliminated.” The “reduced potential” can be used for this purpose, but it is not measurable, and its estimation resurrects the problem of the “surface potential.” It is also argued that none of the methods for “estimating” the absolute potential is “philosophically” distinct from the others, although, in connection with the Kanevski modification, the method involving the direct measurement of the Volta potential between liquid mercury and an electrolyte solution holds the promise of arriving at the best result, even though it is not performed in vacuum.