MIXED-LIGAND CHELATES OF 1-HYDROXYETHYLIDENE-1, 1-DIPHOSPHONIC ACID WITH ALKALINE-EARTH METAL-IONS

The proton-ligand formation constants of 1-hydroxyethylidene-1, 1-diph osphonic acid (HEDP) and its complexation equilibria with alkaline-ear th metal ions involving glycine, beta-alanine, catechol, oxalic acid, 5-sulphosalicylic acid, 1, 10-phenanthroline, 2, 2;-bipyridyl and imin odiacetic acid have been determined potentiometrically in aqueous medi um. Excepting Gly and Ala, HEDP behaves as a secondary ligand in all t he systems studied. The stepwise stability constants, the percentages of relative stabilization values and the distribution of the total met al ions in different chelated species have been evaluated and critical ly discussed.