1967 Volume 40 Issue 9 Pages 2091-2095
The liquid zinc amalgam method was developed as a rapid procedure for the reduction of pentavalent protactinium. Several minutes were sufficient for the complete reduction of 4.2×10−4 M pentavalent protactinium in both hydrochloric and sulfuric acid solutions. The stability of tetravalent protactinium in these media was investigated by spectrophotometry. Re-oxidation occurred gradually, even in the absence of atmospheric oxygen, and amounted to 8% in 15 hr. These results may be understood in terms of the slow rate of the (2Pa4++2H+\ ightleftarrows2Pa5++H2) reaction. The formation of sulfato complexes of tetravalent protactinium was inferred by spectrophotometry with relation to the similarity of the electronic structure between Pa4+(5f1) and Ce3+(4f1).
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