Stability constants of the Pb [II] - ethylenediamine-malonic acid system

Overall stability constants of mixed ligand completes formed by Pb [II] with ethylenediamine and malonic acid have been studied polarographically using the method of Schaap and McMastors. Formation of three complex species, [Pb [en] male]], [Pb [en] [malO2][2]- and [Pb [en]2[malo]] arc observed. The free ligand concentration is calculated from the pH and the total amount present, using the dissociation constants of the ligands. The overall formation constants have been evaluated at 25 degree and an ionic strength of 1.5 [KNO[3]]. The equilibrium constants, computed from the effect of the ligand concentrations en half wave potential are correlated and discussed in term of charge neutralization, statistical consideration etc