Some Observations on the Potential of the Manganese Dioxide Electrode

The potential of the system Pt (or C) , , has been determined with the object of obtaining the standard potential of the ‐manganous ion couple in acid solution. Some electrodes gave values close to those obtained by previous workers and to the thermodynamically calculated value of 1.23 volts. Other electrodes behaved erratically. Similar determinations on oxides with the structure of either γ or of pyrolusite and having compositional differences (varying n values) snowed that the standard potential varied with n. Evidence supplied by electron diffraction pointed to the occurrence of a spontaneous reaction at pyrolusite electrodes independent of the reaction being investigated. In the light of these experimental results, an attempt has been made to explain the conflicting evidence of previous workers.