Solution speciation in the aqueous Na(I)–EDTA and K(I)–EDTA systems

Abstract

Speciation in the aqueous sodium(I) – ethylenediaminetetraacetic acid and potassium(I) – ethylenediaminetetraacetic acid equilibrium systems was investigated by automated gravimetric potentiometric titration. It was found that in both cases, particularly below neutral pH values, speciation includes a previously uncharacterized diprotonated complex. All formation and acid dissociation constants were measured for the full systems. The validity of previous literature equilibrium constants, which are based on incomplete equilibrium models, is discussed.