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An X-ray fluorescence method is described for the analysis of niobotamalate concentrates, bringing speed and accuracy to determinations that are difficult chemically. Many of the problems inherent in the X-ray fluorescence analysis of powdered samples are eliminated by fusion of the sample in a mixture of Li2B4O7 and La2O3. Absolute amounts can be determined without reliance on chemically analyzed standard concentrates. Standards in a wide range of concentrations are readily prepared from pure chemicals. La2O3 plays a dual role, aiding in the fusion of highly refractory oxides and minimizing absorption differences between samples. In addition to niobium and tantalum, elements commonly present in niobate-tantalate ore concentrates, such as titanium, iron, tin, and manganese, are readily determined.The fusion mixture consists of 80 mg of sample, 120 mg of La2O3 and 800 mg of Li2B4O7. The fusion is made in graphite crucibles at 1100°C for 15 min. The cooled bead is ground in a mixer-grinder and pressed into a pellet. X-ray fluorescence measurements yield linear calibration curves for each of the elements over a wide range of concentration.

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