SOLVENT EXTRACTION IN THE SEPARATION OF RARE EARTHS AND TRIVALENT ACTINIDES.

This review is restricted entirely to extraction of elements in the trivalent state. It does not include scandium because of its atypical character, nor plutonium, because applications of solvent extraction to separation of plutonium from other elements are usually based on the relative nonextractability of Pu(III) or on the high extractability of plutonium species in a higher oxidation state. Many publications of systems that may be useful in purifying the trivalent elements by their relative inextractability are ignored, because it is too difficult to establish limits for making choices. All those systems are included in which some of these elements are sufficiently extracted to be useful for analysis or for separation from other elements or from each other.