This book describes studies of evaluation of solution equilibria of heterobinuclear complexes of some bipositive metal ions with iminodiacetic acid (IMDA) and L - Pyrrolidine -2 - carboxylic acid (Proline) as ligands have been evaluated under biologically relevant conditions. The formation and stability of binary, ternary and quaternary complexes have been determined. The formation has been studied potentiometrically by Irving and Rossotti technique. The βpqrst values were evaluated using SCOGS computer program. Distribution curves of the complexes occuring at different pH have been obtain to derive complex formation equilibria.