An instrument has been constructed for chronopotentiometry with current that varies as any selected power of time, tq, where gcan lie anywhere between 0.2 and 5.0. The ambiguity due to charging current is minimized by an initial brief operation at constant current. The determination of reducible species alone or in the presence of other species can be carried out to concentrations as low as 2.5 X M. Relative standard deviations are of the order of 1% at 5 X M.