Neptunium oxide fluorides

Neptunium dioxide, Np03, is the most stable of the neptunium oxides. It crystallizes with the fluorite structure of all the actinide dioxides, with a crystalline density of 11.14 g/cm . It can be formed from the thermal decomposition of other neptunium compounds, such as the hydroxide, the nitrate, or the oxalate, in the temperature range of 600 to 1000°C. High-fired NpOj can be dissolved in hot concentrated nitric acid containing small amounts of fluoride. 

Several preparative methods do not use elemental mixtures. Group IIA-Pt intermetallic compounds have been prepared by reacting platinum metal with the group-IIA oxide under hydrogen or ammonia at 900-1200 C. Beryllium metal reacts with neptunium fluoride under vacuum at 1100-1200°C to form BC 3Np. 

Manganese trichloride oxide, 4141 Manganese trifluoride, 4335 Mercury(II) bromide, 0269 Mercury(I) fluoride, 4312 Mercury(II) iodide, 4602 Molybdenum hexafluoride, 4365 Molybdenum pentachloride, 4180 Neptunium hexafluoride, 4366 Osmium hexafluoride, 4370 Palladium tetrafluoride, 4347 Palladium trifluoride, 4341... 

Neptunium forms a number of halides in various oxidation states. These include tri-, tetra- and hexafluorides of compositions NpFs, NpF4, and NpFe, respectively trichloride, NpCF and tetrachloride, NpCh tribromide, NpBrs and the triiodide NpN. Neptunium fluorides are formed by heating neptunium dioxide at elevated temperatures with fluorine in the presence of hydrogen fluoride. The tetrachloride, NpCh is obtained similarly by heating the dioxide with carbon tetrachloride vapor at temperatures above 500°C. Neptunium tribromide and triiodide are prepared by heating the dioxide in a sealed vessel at 400°C with aluminum bromide and aluminum iodide, respectively. 

All the early work on plutonium was done with unweighable amounts on a tracer scale. When it became apparent that large amounts would be needed for the atomic bomb, it was necessary to have a more detailed knowledge of the chemical properties of this element. Intensive bombardment of hundreds of pounds of uranium was therefore begun in the cyclotrons at Berkeley and at Washington University in St. Louis. Sepa-ration of plutonium from neptunium was based on the fact that neptunium is oxidized by bromate while plutonium is not, and that reduced fluorides of the two metals are carried down by precipitation of rare earth fluorides, while the fluorides of the oxidized states of the two elements are not. Therefore a separation results by repeated bromate oxidations and precipitations with rare earth fluorides. 

Manganese fluoride trioxide, 4295 Manganese tetrafluoride, 4337 Manganese(IV) oxide, 4700 Manganese(VII) oxide, 4704 Mercury(II) bromate, 0269 Mercury(II) nitrate, 4598 Mercury(II) oxide, 4600 Monofluoroxonium hexafluoroarsenate, 0097 Neptunium hexafluoride, 4360 Nickel(II) nitrate, 3583... 

Absorption spectra have been obtained for certain actinide ions which are soluble in saturated KF solution U(IV), Np(IV), Np(V), Np(Vl), and Am(III). Oxidation-reduction reactions of neptunium have been studied. Four new complex fluorides have been prepared and identified by x-ray powder patterns a-K NpFe, pi-K NpFs, KNPO2F2, and K3NPO2F3. Three additional complex fluorides, of Np(III), Np(V), and U(VI), have been prepared but not identified. 

Dissolution of the calcium fluoride in aluminum nitrate-nitric acid oxidizes the plutonium to the tetravalent hexanitrate complex (3), while the transplutonium nuclides remain in the trivalent state. The only actinides retained by a nitrate-form anion-exchange column are thorium, neptunium, and plutonium. The uranium distribution coeflBcient under these conditions is about ten, but uranium should not be present at this point since hexavalent uranium does not carry on calcium fluoride (4). 

The donor action of [NOs]" as an anionic ligand towards thorium(iv) and uranium(iv) in the presence of trimethylphosphine and tris(dimethylamino)phosphine oxide in aqueous media has been found to be very similar. The larger nitrate ion was observed to form more stable species with thorium than the chloride ion whereas in the uranium(iv) case both complexes formed equally readily. A study of the sulphate complexes of uranium(iv), neptunium(vi) and plutonium(vi) in HCIO4-H2SO4 solution showed the stability constants to follow the order U[Pg.453]

The ability to determine oxidation states is demonstrated in Table 2 for the isomer shift data of fluorides of neptunium for various oxidation states represented by the 5f configuration. 

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