In aqueous solution curium exists in the oxidation states Cm(III) and Cm(IV). Solutions of Cm(IV) can be prepared only by dissolving CmF4 in a solution containing a high concentration of fluoride to form the stabilized complexes CmFs~ and/or CmF6 2". As shown by the oxidation — reduction potentials of Table 9.6, Cm(IV) is a strong oxidizing agent. In the absence of sufficient complexing for stability, it is rapidly reduced to Cm(III) under the influence of the alpha activity from curium decay. Trivalent curium forms complexes with СГ, N03", S04 2~, and C2 04 2~ which are less stable than those with americium, but the CNS’ complex of curium is more stable than that of americium. Organocomplexes and chelates are also formed [K2].

242 Cm is recovered from irradiated Am02/Al cermets by dissolution of the aluminum in hot NaOH, followed by dissolution in 6 M HC1. The curium and americium are separated from fission products by anion exchange from 11 M LiCl and elution with 12 M HQ, and the curium is then separated from the americium by selective elution from a cation-exchange column with lactic acid solution [H4].

244Cm is recovered from irradiated Pu/Al alloys and Am02(Pu02)/Al cermets by dissolution, extraction of plutonium with TBP in и-dodecane, extraction of americium and curium from the aqueous raffinate with 50 percent TBP in kerosene, purification of the americium and curium fraction by extraction with tertiary amines, and separation of americium by precipitation of the double carbonate K5 Am02(C03)3 [G5]. A high-pressure ion-exchange system for the separation of curium, americium, and rare earths from feed solutions of dilute HN03 has been applied at the Savannah River Laboratory [HI, L5].