Potentiometric Determination of Stability Constants of Rare-Earth Chelates of 1-Phynyl-1-hydroxy-3-phynyl-2-thiourea

Abstract

Stability constants of the complexes of La{III), Pr{III), Nd(III), Sm{III), Dy(III), Tb(III) and Ho(III) with 1-phenyl-1-hydroxy-3-phenyl-2-thiourea (PHPT) have been determined potentiometrically in 65% (v/v) aqueous dioxane medium. The method of Bjerrum and Calvin, as modified by Irving and Rossotti has been used to find out the values of ñ and pL. The order of the stability constants was found to be:

                                  Ho > Dy > Tb> Sm > Nd > Pr> La