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

A. Discussion of selected references 747log 10 K ((A.68), I = 3M) = 42.79 ± 0.19 recalculated from [90RIG]log 10 K ((A.68), I = 1M) = 42.84 ± 1.06 calculated in the presentreview from [84MAY]Thus for: β 6,3 /β3 3 = K(A.67)log 10 K(A.67, I = 3M) = −(10.06 ± 0.57) recalculated from [90RIG]log 10 K (A.67, I = 1M) = −(8.81 ± 1.08) calculated in the presentreview from [84MAY]d) Normal potential of the Np(V)/Np(VI) redox couple in bicarbonate mediaThe redox potential of the Np(VI)/Np(V) couple measured by Riglet [90RIG, pg. 104]in 0.1MNa 2 CO 3 + 3MNaClO 4 , is accepted in the present review since the methodologyused was checked using the corresponding uranium system and gave reliable dataconsistent with those selected by the uranium review [92GRE/FUG]. It is also in goodagreement with the previous value measured by Simakin [77SIM] and selected by thisreview.[90RÖS/HUN]Electromigration measurements were carried out for Np(V) solutions at 298.1 K, I =0.1 M (perchlorate) in the presence of a holding reductant (NO − 2 or N 2H 4 ,1×10 −3 M).The mobilities began to drop at pH values near 9, and reverse direction near a pHvalue of 11, indicating the formation of an anionic species at high pH. The valueslog10 ∗β1 =−(10.45 ± 0.25) and log10 ∗β2 =−(21.95 ± 0.35) were reported, but theseare probably mixed constants, and are identical to those reported in [87RÖS/MIL](andprobably from the same experiments). See the discussion for [87RÖS/MIL].[90SAW/CHA]This seems to be a partial summary, or a preliminary publication, of Sawant, Chaudhuriand Patil [90SAW/CHA2]. See comments there.[90SAW/CHA2]This is a comprehensive study on the fluoride complexation of Th(IV), U(IV),Np(IV) and Pu(IV), using a fluoride-selective electrode. Preliminary summariesof this study were also published separately by Sawant and Chaudhuri[89SAW/CHA, 90SAW/CHA]. The experiments were carried out at I = 1M(Na,H)ClO 4 and (23 ± 1) ◦ C (“room temperature”). The constants were determined bytitrating the corresponding metal perchlorate solution with a NaF solution. Correctionfor the liquid junction potential was made at each point of the titration curve according