Quantitative description or rare-earth extraction by alkylammonium salts

A model has been devised for solvent extraction of a metal by an associated reagent, which incorporates the possibility that a set of associated forms of the extraction agent and the extracted complex may be formed in the organic phase. The activity coefficients for the organic phase have been calculated within the framework of the general theory of associative equilibria. The quantitative characteristics of the association needed to describe the extraction equilibria have been determined from independent cryoscopic and dielectric data. Extraction constants have been obtained for cerium(III) and europium nitrates, which have been used in calculating the compositions of the extracted complexes. The basic concepts can be used also for other solvent-extraction systems containing associated reagents other than alkylammonium salts