Liquid ion-exchange electrodes as end-point detectors in compleximetric titrations: Part II. Determination of Calcium and Magnesium in the presence of Sodium

Abstract

A calcium-selective electrode was used to monitor EGTA and DCTA titrations of aqueous mixtures of calcium, magnesium and sodium salts. The solution concentrations were selected to span the range of natural waters, and the results were analysed statistically. The pattern of titration curves observed with changing solution composition agreed qualitatively with that predicted theoretically, but the overall potential drop was usually lower than that predicted; end-points were determined by graphical and numerical methods. The technique is suitable for the determination of calcium and magnesium in sea water with an estimated accuracy of 0.5%.