Abstract
A study was made on the method for sensitive and rapid photometric determination of uranium with Arsenazo III.
Uranium(VI) forms Arsenazo III complex in 5 M perchloric acid. It has an absorption maximum at 655 mμ; the molar absorptivity is ca. 7.1×104, and Beer's law holds over the range of 02.0μg U/ml. Zirconium, thorium and rare earth elements also form the complexes with Arsenazo III in the acidic solution, which interfere with the determination of uranium. Uranium, however, can be separated from the elements by 8-quinolinol extraction method.
Uranium is extracted with chloroform as 8-quinolinolate from the solution whose pH has been adjusted to 6.06.5, after masking the interfering elements by an addition of EDTA. Uranium is back-extracted with a definite volume of 0.02% Arsenazo III-5 M perchloric acid solution. The absorbance of the aqueous phase is measured at 660 mμ. In this case, the absorption maximum shifts to 660 mμ, and the molar absorptivity is ca. 6.7×104.
In the determination of uranium, uranium(IV)-Arsenazo III complex is usually used. The complex of uranium(VI) is less sensitive but more stable, than that of uranium(IV). Further, the procedure presented is fairly simple, whereby uranium need not be reduced to the quadrivalent state.
