Metal oxide electrodes as sensors in complexometric titrations

EDTA titrations of lead and manganese, and of some other ions by using these as indicator ions, have been followed potentiometrically with PbO(2) and MnO(2) electrodes. Explanations are put forward for the anomalies observed in the titration curves. With the MnO(2) electrode, formation of an Mn(III)-EDTA complex is responsible for the diminished potential breaks. With the PbO(2) electrode the decrease in the potential break and the distortion of the curves in acid solution may be due to reaction between electrode coating and titrant. The MnO(2) electrode has been used for titrations of Ba(2+) Ca(2+), Cd(2+) and Cu(2+) with errors < 1%.