DETERMINATION OF POLYLIGAND COMPLEXES OF COBALT (II) WITH CITRATE AND PYROPHOSPHATE IONS

Abstract

In the work it is shown by the spectrophotometry method that depending on the concentration ratio of ligands [PPi4–]/[Cit3–] in the pyrophosphate-citrate electrolyte, cobalt (II) ions form not only citrate [Co(Cit)2]4– and pyrophosphate [Co(PPi)2]6–, but also polyligand complexes [Co(PPi)m(Cit)n]+2–(4m+3n). The composition of polyligand complexes [Co(PPi)Cit]5– was determined, and the equilibrium constant of the reaction of their formation and the constant of their stability were calculated (pβ=8.47). The dependence of the degree of formation of citrate, polyligand, and pyrophosphate complexes of cobalt (II) in the pyrophosphate-citrate electrolyte on the logarithm of the ratio of equilibrium concentrations of ligands is calculated.