SPECIATION OF BINARY COMPLEXES OF Co(II), Ni(II), Cu(n) AND Zn(II) WITH ETHYLENEDIAMINE IN ACETONITRILE- AND ETHYLENE GLYCOL-WATER MIXTURES

摘要

Chemical speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with ethylenediamine was investigated pH-metrically in acetonitrile- and ethylene glycol-water mixtures. The stability constants were calculated using the computer program MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The models for the binary species contained ML, ML2 and ML3 for Co(II), Ni(n), Cu(II) and Zn(II) in acetonitrile- and ethylene glycol-water mixtures. The trend in variation of stability constants with change in the dielectric constant of the medium was explained on the basis of electrostatic and non-electrostatic forces. Distributions of the species with pH at different variations (0.0-60.0% v/v) in acetonitrile- and ethylene glycol-water mixtures were also presented.