Reactions between neptunium ions

IONS OF SAME METAL IN DIFFERENT OXIDATION STATES 

A reinvestigation of the rate dependence on [H ] has since been made and it was concluded that the relation 

For sulphate media much more complex rate laws for both the forward and reverse steps of the reaction were found by Sullivan et al. , the observed rate coefficient ( bs) being dependent on both [H ] and [HSO ]. For the forward reaction 

For the reverse process the rate law obtained (sulphate media) was 

46x10 P.mole . sec , 7.39x10 and 1.35x10 mole.l , respectively. Possible transition states have been discussed .  

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The reaction rate is also sensitive to chloride ion concentration. The overall reaction between neptunium(iii) and uranium(vi)... 

Mixed second-order kinetics. Consider an electron transfer reaction between the triva-lent ions of neptunium and iron in aqueous solution 23... 

Recently, the SISAK technique has been applied for the separation of new, neutron-rich neptunium isotopes formed in direct transfer reactions between 8Xe projectiles and targets of Pu at the UNI LAC heavy-ion accelerator. The SISAK system consisted of three mixer-centrifuge units and a degasser. 

A kinetic study has been made of the oxidation of ascorbic acid (H A) by neptunium(vi). The rate law is of the form — d[NpVi]/dr=A 2[H2A] [Np i] with no evidence for a hydrogen-ion dependence over the range 0.05 < [H+] < l.OOM. In aqueous media Np i exists as the [O—Np—0] + ion with between four and six equatorial water molecules. A comparison with the reactions with aquo-ions, e.g. or where inner-sphere reactivity is established and with [Fe(phen)3] + indicates that the preferred pathway is outer sphere. The exchange rate for [(5-nitrophen)gFe] +/ + and the redox potential are both greater than for the Np VNp " couple and these features are considered- the reason for the rate of the present reaction being 40 times slower than that of the iron system. 

The subsequent reaction between hypobromite and bromite has been shown to be rapid, requiring fast reaction techniques for its characterization. The oxidation of neptunium(vi) by hypobromite has been studied in alkaline media, stable neptunium(vn) salts being formed. There is a rate dependence on hydroxide ion concentration, and nickel(n), cobalt(n), or copper(n) ions increase the reaction rate whereas silver(i) or iron(ii) have no effect. 

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