Some Analytical Applications of Controlled Potential Electrolysis

A relatively simple potentiostat is described which automatically performs the function of maintaining the potential of a working electrode constant at any predetermined value during the entire course of an electrolysis. The instrument is applicable with applied voltages and currents of any reasonable magnitude. Its component parts are easy to assemble, it does not require preliminary calibration, and its control sensitivity of ±0.015 v. is ample for the great majority of applications of controlled potential electrolysis. The application of controlled potential electrolysis as a convenient separation technic in connection with polarographic determinations of metals is described, and data are presented which demonstrate the utility of the method in the analysis of the Copper Group metals. As an example of the preparation of organic compounds by controlled potential electrolysis, experiments on the selective reduction of 9‐(o‐iodophenyl)‐acridine to 9‐(o‐iodophenyl)‐dihydroacridine are described. The recently developed technic of coulometric analysis with a mercury cathode at controlled potential is described. Data are presented which demonstrate the accuracy of the method for the determination of copper, bismuth, and lead. The application of the technic of coulometric analysis to the determination of the reduction states that correspond to the polarographic waves in complicated reductions at the dropping mercury electrode is discussed.