An iridium based mercury film electrode: Part II. Comparison of mercury-film electrode behaviors: theory versus reality

An experimental study of a 2 mm diameter iridium based mercury film rotating disk electrode (IrMFE) is presented. Using anodic stripping voltammetry and test ions of cadmium, lead and zinc, the effects of Hg film thickness on peak potential, half-width and peak height are compared with the predictions given by the De Vries and Van Dalen theory. The response of the Ir-MFE was found to be theoretical for Hg film thicknesses less than 1 μm. Application of this classical theory to real Hg film electrodes, on any type of substrate, is found to be inappropriate when the Hg film thickness begins to exceed 1 μm. It is also shown that the stripping peak characteristics at a semi-spherical film electrode can be estimated by assuming that it is composed of a large number of annular flat films. The individual responses of the flat films can be summed to give the overall semi-spherical response.