Back titration with mercuric nitrate in alkaline medium potentiometric estimation of thorium

Summary Mercuric nitrate has proved to be a suitable back titrant for EDTA amounts in excess of those reacting quantitatively with thorium amounts ranging from 46 g up to 25 mg. End points are detected potentiometrically with reasonable jumps amounting to an average of 70 mV per 0.1 ml titrant. Thorium can be determined with fair accuracy, in the presence of double its amount of uranium.