DETERMINATION OF THE COMPOSITION AND STABILITY CONSTANT OF COBALT (II) POLYLIGAND CITRATE-MOLYBDATE COMPLEXES

Abstract

The complex formation of cobalt (II) with citrate (cit3–) and molybdate (MoO42–) ions in 0.3 mol·l-1 Na2SO4 solution at 20°C was studied by spectrophotometric method. It has been established that in a citrate-molybdate electrolyte at pH 9.0, cobalt (II) ions form, depending on the ratio of the equilibrium concentrations of ligands: molybdate [Co(MoO4)2]2–, citrate [Co(cit)2]4– and polyligand complexes [Co(cit)m(MoO4)n]+2-(3m+2n). The composition of [Co(cit)(MoO4)]3– polyligand complexes was determined, the equilibrium constant Ke of the reaction of their formation and their stability constant (lgβMLX = 5.86) The dependence of the degree of formation of molybdate, citrate and polyligand complexes of cobalt (II) in citrate-molybdate electrolyte on the logarithm of the ratio of equilibrium concentrations of ligands was calculated.