INTERPRETATION OF STABILITY-CONSTANTS OBTAINED FROM ELECTROMETRIC DATA FOR ZINC TRIAD CATION ETHANEDIAMINE COMPLEXES IN AQUEOUS-SOLUTION - THE PARADOX OF COMPLEX EQUIVALENCE, THEIR ACID PROPERTIES AND CHELATION EFFECTS

Some basic elements have been developed for the interpretation of stab ility constants of metal-ion complexes obtained from electrometric dat a alone. Zinc triad cation-1,2-ethanediamine systems have been conside red. The paradox of electrometric equivalence of complexes has been di scussed. Relations for electrometric apparently indistinguishable comp lexes have been derived and acid properties of the protonated complexe s and chelation effects have been estimated on the basis of Bjerrum's and Schwarzenbach's empirical relations. The precision of the basic el ectrometric methods (potentiometry with amalgam and Hg electrodes, DC and tast polarography) and its influence on the possibility of the sel ection of a statistically unique model for complexation equilibria has been evaluated. Models including complexation with the monoprotonated form of 1,2-ethanediamine have been refined. A definitive model for c omplexation equilibria of zinc family cations in acid and near neutral aqueous solutions of 1,2-ethanediamine has been proposed.