In the course of an investigation of the oxidation reduction potentials of some organic systems, it was found impossible to obtain concordant measurements by the ordinary methods. Accordingly, we turned to the polarographic method first developed by Prof. J. Heyrovsky of the University of Prague and recently gaining favor in this country. The polarographic method consists of applying, by means of a dropping mercury electrode, a steadily increasing electromotive force to a solution of some substance which can be reduced. Current and voltage are measured and recorded graphically. There is little current increase with respect to voltage until a point is reached where the voltage is sufficient to reduce the substance. The current then rises suddenly until the rate of the reaction becomes steady, when the curve again flattens out to a gentle slope as before. A whole series of reducible substances may be determined from the same solution in this way if their reduction potentials differ by as much as .2 volt
