The Chemistry of Protactinium. II : The Behavior of Pentavalent Protactinium in a Perchloric Acid Solution

Studies of the chemical behavior of protactinium (V) were carried out with the TTA-benzene extraction method, the ion exchange method and the filtration method. When the protactinium concentration is less than 10^M and the perchloric acid concentration is 0.3-2.0N, the reaction of TTA extraction may proceed as : PaO_m(OH)_n^+4HT⇄Pa(OH)T_4+(m+n-1)H_2O+(5-2m-n)H^+ where 2m+n is 3 and 4, or as : PaO_m(OH)_nT^+4HT⇄PaT_5+(m+n)H_2O+(4-2m-n)H^+ where 2m+n is 2 and 3. The cation exchange experiment gives results consistent with this conclusion. On the other hand, when the concentration of protactinium is higher than 10^M, the above relation does not hold, even in the 5N perchloric acid solution, because protactinium forms the aggregates to a great extent. This has been confirmed by the filtration experiment