Analysis for Neptunium by Controlled-Potential Coulometry**AEC Reports HW-58212 and HW-59447. Work performed under contract with the Atomic Energy Commission.††The full text of this paper is not included in the Proceedings because the information contained therein is available in documents numbered HW-58212 and HW-59447.

Electrolytic Preparation of Neptunium Species in Concentrated Carbonate Media

“…This supports the formation of complexes, Np0 2 (C0 3 ) 3~ and Np0 2 (C0 3 )$~, which have been proposed previously [3,6], J£ , 1/2 (VI^V) obtained to be 0.69 V corresponds to β 3 of Np0 2 (C0 3 )f~ which is greater by 11.5 orders of magnitude than that of Np0 2 (C0 3 ) 3~. The reported values for β 3 of Np0 2 (C0 3 ) 3~ show remarkable discrepancy, from 10 8 to 10 16 [7,20,21], and the reported β 3 of Np0 2 (C0 3 )f-is ΙΟ 2115 [1],…”

“…The residue obtained was dissolved in 1 Μ HC10 4 to yield the stock solution of Np(VI), NpC>2 + . The concentration of neptunium in the solution was determined to be 2.09 χ 10" 2 Μ by controlled-potential coulometry [16], and the purity of the oxidation state of neptunium ion was confirmed spectrophotometrically. All other reagents were of reagent grade, and distilled water was used to prepare all solutions.…”

Reduction behavior of neptunium(V) at a gold or platinum electrode during controlled potential electrolysis and procedures for electrochemical preparations of neptunium(IV) and (III)

“…The residue obtained was dissolved in 1 M perchloric acid, and stock solution of NpO 2þ 2 was obtained. The concentration of Np in stock solution was determined by controlled potential coulometry [14] to be 7.91 Â 10 À2 M. The concentrations of NpO þ 2 , Np 4+ and Np 3+ coexisting in the prepared NpO 2þ 2 stock solution were determined spectrophotometrically to be less than 0.4%, 0.05% and 0.1%, respectively, of that of NpO 2þ 2 . The NpO þ 2 solution was prepared from the NpO 2þ 2 stock solution by controlled potential electrolysis at a potential (E) of +0.600 V as described in Section 3.2.…”

“…The NpO 2þ 2 /NpO þ 2 and Np 4+ /Np 3+ reactions have been used for precise electrolytic adjustments of oxidation states of Np or coulometric determination of Np [14,15]. However, since the reduction of NpO þ 2 to Np 4+ or Np 3+ which includes the breaking of an Np-O bond is very slow, the quantitative electrolytic reduction of NpO þ 2 has scarcely been successful except for the reduction of NpO þ 2 to Np 3+ at a glassy carbon [16] or platinum [17,18] electrode.…”

Controlled Potential Coulometry of Metals in Fused Lithium Chloride-Potassium Chloride Eutectic.

“…Studies of two such systems, Cr(III)/Cr(II) and V(III)/ V(II) in the LiCl-KCl eutectic, form a portion of the work described here. The standard electrode potentials of these two systems, previously determined by Laitinen and coworkers (8,10), were also evaluated here using a controlled potential coulometric procedure described by Stromatt, Peekema, and Scott (16). Cozzi and Vivarelli (2, 3) reduced concentrated hydrochloric acid solutions of niobium (V) chloride at a mercury pool electrode to obtain chloro complexes in which the metal exhibited valence states of 4, 3, and possibly 2.…”