1The Research Institute for Iron, Steel and Other Metals, Tohoku University, Sendai
Few methods have been found so far to determine the microamounts of Nb in metal samples without any interferences with Ta. The author intended to propose a chemical method to determine a small quantity of Nb in some metals utilizing the mixed ligand complex of Nb-PDTC-PC. Chloroform-propylene carbonate (4:1) was used as an extractant without any interference with Ta. The complex formation was carried at 8 M HCl in the presence of 1∼3 m \ell of 2% PDTC and 1∼2 m \ell of 1 M PC for 0∼25 μ g Nb(V), the final volume being 30 m \ell . The reaction was completed by allowing the reaction mixture to stand for 20 min. The complex extracted into the organic layer gave the reproducible absorbance at 445 nm and was stable for 20 min. No interference by the presence of 100 mg of Ta and/or Zr was found in the determination of 20 μ g of Nb.
The proposed procedure was applied to the determination of 10-3-0.6% Nb in steel and Ta- and Zr-metals.
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