多量のバナジウムを含有する磁石合金中のクロムの光度定量
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概要
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The spectrophotometric method for chromium with diphenylcarbazide was studied and improved. The improved method proved to be applicable to the determination of chromium in permanent magnet alloys containing large amounts of vanadium.<BR>Phosphoric and hydrofluoric acids are widely used as masking agents of iron(III). Iron (III) in dilute sulfuric acid solution reacted with diphenylcarbazide and showed a pale brown color the absorbance of which was very small at the maximum absorption wavelength of chromium (VI)-diphenylcarbazide. The color of chromium (VI) -diphenylcarbazide was unaffected in dilute sulfuric acid solution by iron (III) in the range of 1 to 4 mg. When phosphoric acid was added, the color of chromium (VI) -diphenylcarbazide in the dilute sulfuric acid solution decreased almost linearly with the amount of iron (III). Vanadium (V) in the dilute sulfuric acid solution containing very small amount of phosphoric acid also reacted with diphenylcarbazide and gave a dense yellow coloration the absorbance of which was almost negligible at the maximum absorption wavelength of chromium (VI)-diphenylcarbazide. Therefore, in the presence of phosphoric acid, the developed color of chromium decreased linearly with the amount of vanadium, because vanadium (V) combined steadily with diphenylcarbazide.<BR>In the absence of phosphoric acid, however, the color of chromium (VI)-diphenylcarbazide in dilute sulfuric acid solution was unaffected by any amount of vanadium (V). Nickel and cobalt gave no effect on the coloration.<BR>The calibration curve was prepared on dilute sulfuric acid solution of chromium containing only 2 mg of iron (III). Beer's low was obeyed up to 100 μg of chromium.<BR>The proposed method compared with the ferrous-permanganate titrimetry had a higher reproducibility, and the procedure was simple and rapid.
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