The inflection point of the variation of interionic distance between Sm3+ and Cl− in a methanol and water mixture

Abstract

The stability constants, β1, of the monochloride complex of Sm(III) have been determined in mixed system of methanol and water at 1.00 mol dm−3 ionic strength using a solvent extraction technique. The values of β1 increase with an increase in the mole fraction of methanol (X s ) in the mixed solvent system when 0≤X s ≤0.351. The interionic distance of Sm3+−Cl− (d Sm−Cl) in the mixed solvent system was estimated by applying the Gibb's free energy derived from β1 to a Born-type equation. It was determined that an inflection point of the variation in the estimatedd Sm−Cl againstX s was present in the vicinity ofX s =0.054. The inflection point ofd Sm−Cl shows a value ofX s between those ofd Eu−Cl andd Nd−Cl previously obtained by us.