Sequential determination of plutonium and uranium by potentiometry

A potentiometric method has been developed for the determination of uranium and plutonium in the same aliquot. First plutonium is converted to Pu(VI) by perchloric acid oxidation. This is then reduced to Pu(IV) by the addition of excess of Fe(II), which is then titrated against standard potassium dichromate. The resulting solution is evaporated to a small volume and uranium is determined by modified Davie's Gray's method, in which uranium is reduced to U(IV) by Fe(II) in phosphoric acid medium. The excess Fe(II) is destroyed and U(IV) is titrated against standard potassium dichromate. For 3 to 5 mgs each of uranium and plutonium a precision of 0.4% and 0.2% is respectively obtained and the accuracy is within precision limits. (author)