NARROW SPAN COULOMETRIC ANALYSIS OF NEPTUNIUM

A narrow span (E(O)' +/- 0.1 V) controlled potential coulometric metho d has been developed for the determination of neptunium in 1M H2SO4 wi th a RSD of 0.2%. The main advantage of this method over the existing coulometric methods is that it can tolerate up to a 5-fold excess of p lutonium. The method involves carrying out the electrolysis to about 9 7% and calculating by an iterative computation the formal electrode po tential in situ, which is used to calculate the total amount present i n the sample. The method consists in oxidation of all the neptunium to Np (VI) by Ce(IV), destruction of excess Ce(IV) and reduction of Np(V I) to Np(V) by NaNO2, destruction of excess nitrite by sulfamic acid f ollowed by coulometric titration of Np(V) to Np(VI).