吸光々度法による合金鋼中のニオブ,タンタルの定量

概要

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As a method of analysis of niobium and tantalum in alloy steels, the spectrophotometric determination by use of pyrogallol has been investigated. Containing tungsten in sample, the precipitates was ignited to convert it into oxide and treated with dilute alkali to remove tungstic acid. Since the separation of titanium is difficult, a method of determination in the presence of niobium, tantalum and titanium has been used. Although the maximum absorption of Nb-pyrogallol complex showed at 380 mμ and that of Ta-pyrogallol complex at 400 mμ, the result of investigation revealed that using of the absorption at 430 mμ for Nb-pyrogallol complex was convenient as the maximum absorption remained constant with pH 6.57.5, while it decreased with an increase of acidity. The absorption of Ta-pyrogallol complex was the highest with pH 2. 1 and the value were less with the increase or decrease of the pH. The light absorbency of Ta-pyrogallol complex was influenced by the change of temperature and its correction was made by use of a factor ± 0.0015 /°C/mg Ta. Determination of niobium and tantalum in alloy steel by this method gave a satisfactory result.
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