The usually employed expression for the Tafel slope is modified to take into account the potential which is effective in charge transfer within the double layer. The exchange currents and cathodic Tafel slopes are obtained on noble metal electrodes having different number of holes in the d‐band. Using the conventional and modified Tafel slopes, possible paths and rate‐determining steps are suggested for the cathodic reduction of oxygen.

A study has been made of the reactivity of pure aluminum with iron sulfate in solutions of varying acid strength. Electrode potentials, weight loss data, and polarization curves are presented, and it is shown that the reaction may be interpreted from an electrochemical point of view. The analysis of the behavior is based on the previously developed theory of the “mixed potential”.

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A study has been made of the reactivity of pure aluminum with cerium+4 sulfate in sulfuric acid. Electrode potentials, weight loss data, and polarization curves are presented, and it is shown that the reaction may be interpreted from an electrochemical point of view. The theory of the “mixed potential” is suggested as a more generalized concept than the local cell idea for the interpretation of the dissolution process. A brief outline of a probable mechanism for the dissolution and passive behavior of aluminum is presented.

An experimental study has been made of the polarization characteristics of the following oxidation‐reduction electrode systems: iron sulfate, iron chloride, potassium ferrocyanide‐ferricyanide, and cerium sulfate. Data are presented which strongly indicate that the overvoltage includes an activation overvoltage in addition to that due to concentration polarization. The data are analyzed from the point of view of rate processes and it is shown that the electrode behavior is given by an equation which allows an evaluation of the exchange current density and the transfer coefficients.