The glass electrode — applied electrochemistry of glass surfaces

Abstract

The glass electrode has attained a high standard of construction and application during the almost eighty years of development. The understanding of its functioning, however, has been much slower, and its history represents an example of highly advanced thermodynamics rather than of applied electrochemistry of glass surfaces. Thus, the generally accepted, purely thermodynamic, ion exchange theory cannot give any information about the ionic mechanism of potential formation. From detailed information on glass surfaces by modern surface-analytical methods we have recenttly concluded a “dissociation mechanism”, which is based on the equilibria of functional groups at the glass surface and ions in contacting solutions. This mechanism and several phenomena at the glass surface are described on the basis of electrode kinetics in this paper, and it is proposed to develop methods of measuring kinetic data, e.g. equilibrium exchange current densities of protons and alkali ions between the glass surface groups and the solution. These data, if availbale and in connection with information from other surface-analytical methods, could prove the ionic equilibria at the glass—solution-interface and thus state the dissociation mechanism, elucidate unanswered questions, e.g. the cause of the response time of glass electrodes, and also contribute to the investigation of the fundamental processes of glass corrosion.