AMINES AS EXTRACTANTS--SURVEY OF THE DESCRIPTIVE AND FUNDAMENTAL EXTRACTION CHEMISTRY

Both the study and the use of extractions with highmolecular-weight amines (including quaternary ammoniums) in organic solution are increasing extensively. While equilibria have been measured in the extraction of an increasing range of acids and Aetal ions, a difficulty remains unresolved in that the amine concentration powerdependence of extraction often indicates a different stoichiometry of the complex existing in the organic phase than do limiting loading and other considerations. Nevertheless, amine extraction serves as a useful tool in studying complexes formed in aqueous systems. Process applications have progressed especially in nitrate and chioride systems, in addition to the sulfate systems first emphasized. Systematic surveys, together with information accruing from process development, have extended the ranges of extractions that can be correlated in usefully generalized patterns, which in turn should accelerate the development of new applications. However, many more areas remain to be surveyed before the many pertinent variables will have been covered. New amines of all classes have become available at commercial, development, or researchsample levels, while a few previously promising amines have become less available. Descriptions and current sources are reviewed. (auth