Abstract: | It has been known for some time that the pre-treatment of platinum electrodes often effects subsequent electrochemical reactions. Part of the effect of pre-treatment is due to the fact that anodized or chemically oxidized platinum electrodes become coated to some degree with a film of platinum oxide. This work was concerned with quantitative measurement of kinetic parameters as a function of the extent of oxide film formation. Whenever possible, variations in reaction mechanisms are proposed. Most of the experimental evidence has been taken from current-potential curves but the techniques of chronopotentiometry and microscopy were also used. The reduction of vanadiumV chromiumVI, arsenicV, iodate and oxygen were investigated as well as the oxidation of vanadiumIV, arsenicIII, oxalic acid, and formic acid. The presence of the platinum oxide film effected the reactions studied in a variety of ways but in every case some variation in the kinetic parameters of the reactions studied was recorded. For a number of cases, a modified oxygen bridge theory was found useful. |