Americium Titration Methods

Abstract

To determine americium, we use either of the following methods: spectrometry at 60 keV, spectrophotometry of Am (III) at 503 nm or isotopic dilution mass spectrometry. These methods need reference materials. Now only certified for activity materials exist. So we developped titrimetric methods. The first is an original redox method. After quantitative oxidation to Am (VI) at once by persulfate and argentic oxide, we mix rapidly equal parts of the solution with different knowned quantities of Fe (II) and dilute with molar perchloric acid until fixed volume. Then we measure the Am (III) absorbance and infer its molar extinction coefficient and the americium concentration. The second method is complexometry with EDTA: americium takes the place of mercury in the HgY^2- complex and the quantity of free mercuric ions is determined by pulse coulometry. We work in hexamethylene-tetramine medium at pH 5,5 or in ammonia medium at pH 9,0. The results agree in a 2% range. We give obtained molar extinction coefficients.