SUBJECTS neptunium

The recent photochemistry interests at Oak Ridge have been turned to an examination of these aspects for neptunium in perchloric (15) and nitric acid (16) solutions. A perchloric acid medium provides a much simpler starting point because the CIO ion is not subject to photolysis as is the NO ion when exposed to light of 250-360 nm wavelength. Nevertheless, nitric acid media were ultimately examined because of their obvious practical importance. 

Synthesis of neptunium exhibited a significant feature which was to prove typical for syntheses of all transuranium elements (and other synthesized elements, too). First, one isotope with a certain mass number was synthesized. For neptunium this was neptunium-239. From that time it became a rule to date a discovery of a new transuranium element by the time of reliable synthesis of its first isotope. But sometimes this isotope proved to be so short-lived that it was difficult to subject it to physical and chemical analyses let alone find a useful application for it. A study of a new element would best be conducted with its longest-lived isotope. In the case of neptunium this was iieptunium-237 synthesized in 1942 in the following reaction ... 

Initial studies of the chemistry of neptunium and plutonium actually preceded the official establishment of the Manhattan Project. But as soon as the project got underway, they became the subject of intensive investigation at several of the Manhattan Project laboratories (Seaborg and Katz 1954). Both elements turned out to have four major oxidation states -F3, -F4, -F5, -F6, similar to uranium, hut plutonium is unique in that these four states can all exist simultaneously in aqueous solution. Microchemical techniques were applied to prepare and study microgram quantities, such as the first weighahle sample of a man-made element, 2.77 ig Pu02, in September 1942 (Cunningham and Wemer 1949). At the Los Alamos Laboratory, chemists and metallurgists learned to produce metallic plutonium and studied its complex properties, which eventually turned out to involve no less than six allotropic phases, more than any other element. 

The oxidation, states of neptunium have bean the subject of some question. 

The oxidation states of neptunium have been the subject of some questlon.322... 

There are three solid phases that have been identified for neptunium(V) where solubility data exist (see Table 9.13). These phases are Np020H(am), Np020H(s) and Np205(s). The first two phases have been the subject of a number of studies, and data have been acquired at both fixed and zero ionic strength. The latter phase has only been the subject of a single study. 

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