STEADY-STATE VOLTAMMETRY OF STRONG AND WEAK ACIDS WITH AND WITHOUT SUPPORTING ELECTROLYTE

Voltammetric reduction of perchloric, phosphoric, acetic, and ascorbic acid was investigated under steady-state conditions at platinum- and gold-disk microelectrodes. The dependence of the wave height of proton in perchloric acid on the concentration of supporting electrolyte (lithium perchlorate) was compared with the theory for currents limited by migration and diffusion. The wave height depends linearly on hydrogen ion concentration without and with supporting electrolyte up to 0.04 and 0.08 M, respectively. Also, acetic and ascorbic acids exhibit linear calibration plots with current proportional to concentration of undissociated acid up to 0.1 M. This is as would be predicted for reduction of proton subsequent to fast dissociation of the acid. The fairly well-defined limiting current for dihydrogen phosphate indicates that weak acids with pK(a) in excess of 7 are accessible to voltammetric investigation.