Spectrographic determination of the rare earths in high-purity graphite.
A spectrographic method has been developed for determination of the rare-earth elements in graphite. The rare earths are concentrated from ignited graphite on a calcium base. The impurities (Fe, V, Mn, Al, Ti) associated with the rare earths are separated by precipitation of the rare earths as hydroxides in the presence of Fe as a carrier, followed by precipitation of the rare earths as oxalates in the presence of Ca carrier. The mixture of calcium and rare-earth oxides obtained after ignition of the corresponding oxalates is mixed with graphite in 1:1 ratio and excited in a 15-A d.c. arc, with Nd as internal standard. The concentration ranges of determination are as follows: 0.006-0.125 ppm for Eu, 0.006-0.25 ppm for Gd, 0.006-0.06 ppm for Dy, 0.06-0.5 ppm for Sm. This sensitivity is achieved with 35-g samples of graphite. Higher enrichment factors are needed in order to enhance the sensitivity of the method.
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The Boris Kidrich Institute of Nuclear Sciences, Belgrade, Yugoslavia.