Coulometric determinations

Two methods for performing coulometric determinations have been developed. Either the precise time of duration of the electrolysis is measured or the voltage is controlled. An indicator is necessary for the first method, while the end-point can be determined by the drop of the generator current to the so-called “background current” in the alternate way.The constant current method usually requires amperometric indication, which may give an incorrect end-point when conditions are not completely suitable. Chemical indicators can sometimes be used. The controlled potential method requires, no indicator, but a good coulometer and an instrument for retaining constant voltage are necessary.Coulometric determinations are based on the reactions of the substances to be determined with halogens, using different oxidizing or reducing agents, and with acids or babes.The degree of accuracy obtained using coulometric titrations corresponds to the volumetric analysis results. In addition, however, coulometry may permit an even greater accuracy, when applied under the proper conditions.The major advantage of coulometry consists in the case, with which, within the limits of the reaction, micro-quantities of the reacting substances can be determined.