OXIDATION OF CERIUM(III) DURING SOLVENT-EXTRACTION WITH BENZOYLTRIFLUOROACETONE INTO CARBON-TETRACHLORIDE IN THE ABSENCE AND PRESENCE OF TETRABUTYLAMMONIUM IONS

Cerium(III) in aqueous 0.1 mol dm-3 sodium nitrate solutions was extracted with benzoyltrifluoroacetone (Hbfa) into carbon tetrachloride in the absence and presence of tetrabutylammonium (tba+). In the absence of tba+, only the Ce(bfa)3 was extracted; in its presence, however, not only was the ternary complex (Ce(bfa)4-tba+) also extracted, and the extraction was much better. When the two-phase agitation was continued, the organic phase gradually changed from colorless to brown in the absence of tba+ due to the oxidation of the metal ions in the complex in the organic phase to the cerium(IV). However, in the presence of tba+, the organic phase remained colorless for along time and, thus, oxidation of the cerium(III) was negligible. The rate of oxidation of cerium(III) in the Ce(bfa)3 complex in carbon tetrachloride to the cerium(IV) by forming the Ce(bfa)4 complex was measured by spectrophotometry. The rate of this oxidation was found not to be affected by the ligand concentration,