The determination of niobium, molybdenum, tungsten, iron and titanium in tantalum metal is described. After dissolution of the metal a d extraction of the tantalum by a chromatographic method using tributyl phosphate, the trace elements are determined on thin-film samples by x-ray fluorescence spectrometry. The thin-film samples are prepared either by spotting the sample solutions directly on to filter-paper or by coprecipitation with indium. The limits of detection on the thin film are 0.05-0.7 pg, depending on the element being measured.

This paper describes the development of an accurate, precise, and rapid analytical procedure using x-ray-fluorescence spectrometry for the determination of Nb, Ta, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Zr, and Sn in a wide variety of materials resulting from the processing of Ta-Nb-Sn slags to produce Ta-Nb oxides. The method involves evaporation of all the liquids to dryness, a 1:8 fusion of the solid materials with a flux consisting of Na-Li tetraborate and Na2CO3, and the addition of La oxide as a heavy absorber. With the use of a computer program, residual matrix effects are corrected for by influence-factor calculations.

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A method is presented for the rapid (15 to 20 min) analysis of activated carbon from carbon-in-pulp (CIP) plants for its gold content. The method involves the use of microprocessor-controlled energy-dispersive x-ray-fluorescence spectrometer, using excitation by the radioactive isotope 218Pu, and a background-ratio technique to correct for small variations in the matrix. The gold can be determined in dried granular carbon and milled carbon, provided that the calibration standards and samples are in the same physical form. It is shown that, because of the large differences in composition of the matrices of loaded and eluted carbon, two calibration curves need to be established, one for gold concentrations lower than 200 μg/g, the other for gold concentrations higher than 200 μg/g. The calibration curves for milled carbon showed less scattering of the calibration points than those for granular carbon, and the relative standard deviation of the results for milled carbon was 1% as against 2% for granular carbon.

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