On the Determination of Niobium in Heat Resisting Steel by the Spectrophotometric Method

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  • 吸光光度法による耐熱鋼中のニオブの定量
  • キュウコウ コウドホウ ニ ヨル タイネツ コウ チュウ ノ ニオブ ノ テイリョウ

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Abstract

This experiment was conducted on the spectrophotometric method with xylenol orange, for the purpose of establishing a simple and accurate determining method for obtaining the amount of niobium in heat resisting steel.<BR>First of all, the condition for the formation of the xylenol orange complex salt of niobium was studied. Next, the effect of the coexisting elements was determined experimentally, and the procedure was decided.<BR>The xylenol orange complex salt of niobium is formed quantitatively in a short period in a tartaric acid solution of pH 3.00∼3.35 by heating in a boiling water bath. The absorption maximum of this complex salt is at 530∼565 milli microns.<BR>In this experiment, the absorbance was measured at 565 milli microns. At this wavelength, the relation between the amounts of niobium and the absorbance followed Beer’s law in the range from 0.00 to 0.25 mg/100 mL of niobium.<BR>In this method, there is no significant effect even in case 0.5 mg each of chromium, cobalt, tantalum and titanium, 0.1 mg of copper, 3 mg of iron, 1 mg each of manganese and nickel, 10 mg of molybdenum, and 20 mg of tungsten are contained in the separated sample solution. Aluminum, vanadium and zirconium interfere markedly.<BR>Potassium pyrosulfate which is used for the fusing of niobium pentoxide will be harmful. However, this effect appears constant in the range from 0.4 to 0.6 g in the separated sample solution.<BR>As a result of the experiment, the author succeeded to establish a method in which 0.1 to 5% of niobium in heat resisting steel can be measured easily and accurately. The amount of niobium in actual samples was measured by this method with satisfactory results.

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