Thermodynamics of solid-state connected ion-sensitive membrane electrodes: The silver-silver chloride system: Part I. Standard potential EM0 at 25, 50, and 75°C

Standard potentials E_M⁰ at 25, 50 and 75°C of all-solid-state silver-silver chloride ring membrane electrodes (Schott) with pressed-in silver foil have been measured with respect to the Pt, H₂ electrode by means of a cell without transference (see also [1]) applied earlier by Bates and Bower who measured standard potentials E⁰ of corresponding electrodes of the 2nd kind. The data evaluated by the extended Debye-Hückel theory can directly be compared with the reported 2nd kind electrode data. Identical thermodynamic behavior of both electrode types is observed; small differences (<1.5 mV) of standard potentials and their temperature dependence are discussed on the basis of different states of electrode materials orignating from different electrode preparation and are applied to calculate thermodynamic data of membrane electrodes referred to those of electrodes of the 2nd kind. The results and contradictory literature data are discussed. A brief characterization of membrane and 2nd kind electrodes is given.