Citrate Complexes of Alkaline Earth Metals in Aqueous, Acetone-Water and Ethanol-Water Solutions

[摘要] Formation of the complexes of alkaline earths with citrate ions in aqueous, acetone-water and ethanol-water solutions was studied at room temperature by the equilibrium exchange technique. This technique involved the measurements of distribution of radioactivity between cation exchange resin and solution phase after the radioactive metal ions were equilibriated with the cation exchange resin in the presence of citrate ions (Cit3-) of varying concentrations. The pH of the solutions was controlled to 7.2-7.5, and the ionic strength of the solutions was kept at 0.10-0.12. The present study revealed that both barium and strontium ions formed the one to one citrate complexes, [M Cit]- in all solvent systems examined. It was also observed that calcium ions formed the one to one citrate complex in aqueous solution. In acetone-water and ethanol-water solutions, however, calcium ions were observed to form both one to one and one to two complexes, [Ca Cit]- and [Ca Cit2]4-. The results of the present study indicated also that relative stabilities of the complexes increased in the order; Ba++ < Sr++ < Ca++, and in the order of increasing concentration of the organic components in the mixed solvent systems.

[学科分类] 化学（综合）