chemical thermodynamics of neptunium and plutonium - U.S. ...

248 12. Neptunium group 14 compounds and complexesFigure 12.5: Predominance diagrams of Np(V) carbonate aqueous complexes at differentionic strengths in NaClO 4 aqueous solutions. The lines are calculated with dataselected in the present review. The directly measured stepwise formation constants arealso marked on the figure. Ionic strength corrections can be less than the scatter in thedata. At high ionic strengths, the species NpO 2 (CO 3 ) 3−2has a very small region of predominance,while NpO 2 (CO 3 ) 5−3can be formed only in high ionic strength solutions.The domain below the line [CO 2−3 ]=0.5[Na+ ] cannot be reached experimentally; theline itself correspond to pure Na 2 CO 3 .8.006.00NpO 2+log 10 K i = −log 10 [CO 32-] (mol . l -1 )4.002.00NpO 2 CO 3-NpO 2(CO 3 ) 23-NpO 2 (CO 3 ) 35-0.00-2.00log 10 K 1 (selected data)log 10 K 2log 10 K 3log 10 K 1 (other published data)log 10 K 2log 10 K 3[CO 32-] =0.5[Na + ]0.00 2.00 4.00 6.00[NaClO 4 ](mol . l -1)