The Chemistry of Protactinium. VII. : The Stability of Protactinium (V) in Perchloric Acid and TTA-Benzene Solutions

With a view to understand the reasons for the confusion in published works as to the chemical behavior of protactinium (V) in a perchloric acid solution, the effect of the contact time and the stability of the perchloric acid solution of the pentavalent protactinium in the TTA-benzene extraction have been investigated in relation to the methods of preparing the solution. Four sample solutions, prepared by various methods, were used, and definite differences among them were observed. Two of them have been confirmed to be very stable and not to suffer a change in their distribution ratios with the time of standing, while the others are unstable-that is, their distribution ratios decrease with standing, thereby reaching a constant value which agrees with that of the former two. However, the value consistent with that obtained from backward extraction is not this constant value but the value obtained from fresh solutions of the latter type. Protactinium species in the TTA-benzene solution are also not stable,...