Instrumentation for charging current compensation in d.c. polarography

It is shown that the non-linear charging current in d.c. polarography can be fairly well compensated by a method (suggested by Barker), which consists in applying a small a.c. voltage to the polarographic cell, rectifying the a.c. response, integrating it and subtracting a suitable fraction from the total d.c. response. An instrument incorporating such an automatic compensation for the nonlinear charging current is described. Results obtained with this instrument are presented to show that the limit of measureable concentrations is about 10^?7M for reversible waves and the precision is ±2.5 to ±3.0%. It is possible to obtain, with the instrument described here, well defined polarograms even when the supporting electrolyte concentration is low.