Study of heterogeneous equilibria in solutions of EDTA complexes of copper(II), zinc(II) and cadmium(II)

Abstract It has been established that from the solutions of copper(II)-, zinc(II) and cadmium(II)-EDTA complexes, respectively, in the presence of potassium nitrate and at pH-values lower than 3.5, compounds of the general formula KH 3 (MeY) 2 are precipitated. The corresponding heterogeneous equilibria have been studied at I = 1M and t = 25°C, by application of three independent methods, using the formation function, by means of the solubility of the complex and by determination of the protons bound to the complex in the solution. The results obtained were in agreement. Using the equilibrium constants determined in the heterogeneous systems, the protonation constants of the corresponding metal(II)-EDTA complexes in the homogeneous systems have been calculated. The calculated values were in accordance with those obtained earlier by us in homogeneous systems[1].