プルトニウムと共存するウランの電位差滴定

概要

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A method of Davies and Gray for the determination of uranium has been improved. Air oxidation of uranium(IV) can be avoided by the addition of vanadium(IV) prior to titration (Table I). Plutonium does not precipitate if the sulfuric acid concentration during titration is greater than 1.5 M. A sample containing 50 mg of uranium is dissolved. in nitric-hydrofluoric acids and the solution is evaporated to 3 ml. After addition of 0.5 ml of 2 M sulfamic acid, 10 ml of 14.5 M phosphoric acid and 1 ml of 0.5 M iron(II) sulfate, the solution is allowed to stand for one minute. Seventeen ml of 9 M sulfuric acid, 3 ml of 4 M nitric acid-0.1 M sulfamic acid mixture and 1 ml of 1% ammonium molybdate solution are added to the solution, which is permitted to stand for at least one minute. Adding 1 ml of 0.4 M vanadyl(IV) sulfate, the solution is diluted to 100 ml with water and potentiometrically titrated with 0.1 N potassium dichromate. Data in Table II for synthetic uranium-plutonium solutions show a relative standard deviation of 0.1 to 0.3%. Uranium was also determined in actual samples of 590% uranium-plutonium mixed oxides (Table III). The results agree well with those obtained by another method.
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