The outersphere complex of EuCl2+ in a mixed system of methanol and water of 1.0M (H, Na) (Cl, ClO4)

Abstract

The stability constans,β1, of each monochloride complex of Eu(III) have been determined in the methanol and water mixed system with 1.0 mol·dm−3 ionic strength using a solvent extraction technique. The values ofβ1 increase with an increase in the mole fraction of methanol (X S ) in the mixed solvent system when 0≤X S ≤0.40. The, distance of Eu3+−Cl− in the mixed solvent system was calculated using the Born-type equation and the Gibbs' free energy derived fromβ1. Calculation of the Eu3+−Cl− distance and the preferential solvation, of Eu3+ by water proposed the variation of the outersphere complex of EuCl2+ as follows: (1) [Eu(H2O)9]3+Cl−, [Eu(H2O)8]3+Cl− and [Eu(H2O)7(CH3OH)3+Cl− inXS≤0.014, (2) [Eu(H2O)8]3−Cl− and [Eu(H2O)7(CH3OH)]3+Cl− in 0.014<X S <0.25 and (3) [Eu(H2O)7(CH3OH)]3−Cl− and [Eu(H2O)6(CH3OH)[23+Cl− in 0.25<X S ≤0.40.