In 1N HClO4 and in 2N H2SO4 , “oxygen” uptake on Au electrodes begins at 1.25V vs. NHE. Using a roughness factor of 1.4, monolayer coverage (600 µcoul/cm2) is reached at 1.45V; a second monolayer is completed at 1.75V. Oxygen, once adsorbed, is removed at approximately 1.3V. Thus, the kinetic parameters of the Ce(III)/Ce(IV) reaction in 1N HClO4 and in 2N H2SO4 can be obtained at oxygen coverages θ=1.5–2.0 and θ=0.7–2.0 , respectively. Apparent exchange current densities, ioa , were obtained from low overvoltage data false(≤10 normalmVfalse) . The charge transfer coefficient, α=0.65±0.06 , was determined from the slope of plots of log ioa vs. equilibrium potential. It is independent of oxygen coverage in the range indicated. The apparent rate constant, koa , was calculated from ioa and α normalto be koa≈3×10−4 normalcm/sec in the range 1≤θ≤2 false(1.5≤θ≤2.0 in HClO4false) . Extrapolation of the data to θ=0 yields koa≈12×10−4 normalcm/sec . This change in koa can be interpreted as a change in the potential across the inner double layer which appears as a change in φ2 , normalΔφ2=7.9 normalmV . It appears that up to θ=1 , oxygen adsorbs uniformly and is an excellent electronic conductor which simply serves as an extension of the electrode surface. The constancy of koa normalat 1≤θ=2 indicates no changes in the over‐all structure of the interface in this region.