The Quantitative Spectrographic Analysis of the Rare Earth Elements* III Determination of Major Constituents in Complex Mixtures

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Abstract
Spectrographic methods applicable to the determination of major rare earth constituents in complex mixtures are described. The specific examples discussed are the determination of yttrium and gadolinium in the concentration range of 10 to 100 percent. The procedures involve the high current d.c. arc excitation of rare earth oxide sample-ceric oxide-graphite mixtures. Selected lines of cerium are used as internal standards. The choice of cerium as internal standard was based on the relative ease with which any cerium, if present in a mixture, could be preferentially separated from the mixture and then reintroduced in a standard amount. Precision studies show a standard deviation of about ±2.5 percent for single determinations. The results from a quantitative study of (a) vaporization rates, (b) intensity diagrams of the internal standard line pairs along the longitudinal axis of the arc discharge, and (c) the effect of large changes in excitation conditions on the intensity ratios show that this high precision can be attributed to a high degree of internal standard compensation of excitation variables.

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