Determination of Traces of Certain Rare Earths in Uranium Compounds by Ion Exchange and Spectrography

An ion exchange separation followed by a spectrographic determination has been developed for certain of the rare earths present in uranium compounds. This method permits the determination of dysprosium, erbium, europium, gadolinium, neodymium, samarium, and ytterbium at concentrations as low as 0.01 to 1 ppm. Hydrofluoric acid solutions of uranium containing the rare earth elements, with yttrium as an internal standard, were passed through a cation exchanger. The negatively charged uranium fluoride complex passed through the column while the rare earths were retained. After the residual uranium was completely removed by eluting with 2.5 M hydrofluoric acid, the resin bed was ignited, and the resulting ash analyzed spectrographically for the individual rare earth elements. Other cations which separate with the rare earths were easily separated, when necessary, by standard, wet chemical, group separations The standard deviation for the method was about 10%.