Application of various electrodes in potentiometric titration of calcium

In complexometric titrations various indicator electrodes may be employed for monitoring the course of titration and for detection of the end-point. Several of them, including the silver, mercury, bivalent cation membrane, calcium membrane and manganese dioxide electrodes were investigated and compared in their usefulness. As titrant, EDTA was mostly used, but results with similar chelating titrants were also obtained. The practical utility of the electrodes in titrations depends on their selectivity, magnitude of the end-point break and precision in determination of the end-point. For the electrodes studied, in some instances there is good correlation between the theoretical and experimental titration curves, but it is not always possible to predict the electrode response in the low activity range. In other cases poor correlation does not mean that reasonably good analytical results may not be obtained.