A Rotating Hanging Mercury-Drop Electrode

Abstract

THE work of Gerischer¹ and Delahay et al. ² suggested to us the use of the hanging mercury-drop electrode as a rotating electrode. This electrode, used as a stationary electrode (as proposed by Ross et al. ³), offers several distinct advantages over the conventional dropping-mercury electrode. The charging current is largely reduced, the current-voltage curve can be scanned in a shorter time and the curve-distorting oscillations are eliminated. However, used as a rotating electrode its advantages are even greater. The electrode owes its greater sensitivity to the accelerated diffusion of reducible species (thinner diffusion layer). Peak-formation in the current-voltage curve is prevented, because depletion of the reducible species in the diffusion layer of the electrode cannot occur. If desired, the curve can be plotted manually: it resembles the polarogram in its ideal form. Analysis of multicomponent systems offers none of the extra difficulties encountered with the stationary type³, and compensation of the diffusion current of a more noble metal ion, preceding the diffusion current of the metal ion to be determined, is therefore possible. The reproducibility of repeated determinations on the same solution is comparable to or better than that of conventional polarography. It is possible to determine concentrations of reducible ions as low as 10⁻⁷ M.