ELECTROCHEMICAL BEHAVIOR OF URANIUM IN ANHYDROUS FLUORIDE SOLUTIONS

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Convenient methods have been developed for spectroscopic and electrochemical studies of uranium in anhydrous hydrogen fluoride saturated with cesium fluoride, anhydrous HF-CsF.This solvent exhibits and extended anodic potential limit (2.4 V vs. Cu/CuF_2 or 2.2 V vs. SCE at a Pt electrode) over that for water, and provides high solubility for UF_4. Solubility studies included selected lanthanide and actinide salts and oxides. It was found to be a useful solvent for studies on the various oxidation states of uranium. Uranium displayd spectroscopic and electrochemical behavior in anhydrous HF-CsF medium which was quite different from that in aqueous solutions. The oxidation of U (IV) to U (V) in anhydrous hydrogen fluoride which was not completely saturated with CsF was accomplished by simply heating the mixture. Cyclic voltammograms of the U (V) /U (IV) couple were recorded at Pt and Ni vs. Cu/CuF_2 reference electrode. The U (VI) /U (V) and U (VI) /U (IV) couples were also investigated by means of controlled-potential electrolysis. Uranium (V) apprently exists as UF_6^- in anhydrous HF-CsF.This is in contrast to aqueous solution where the U (V) species is konwn to exist as the UO_2^+ ion.