分別抽出法による銅地金中の微量のリンおよびヒ素の比色定量法

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Phosphomolybdic acid and arsenomolybdic acid are fractionally extracted with organic solvent and their colorimetric method of estimatio has been investigated. Usual method of quantitative determination of phosphorus and arsenic by estimating the light absorbancy in near ultraviolet region after extraction of heteropoly acid with organic solvent is much influenced by the presence of coexisting ions and oxidizing agent, etc. In order to avoid these effects, the author obtained a good result by adding stannous chloride solution as a reducing agent to the solvent layer after fractional extraction to develop molybdenum blue. In this method, phosphomolybdic acid and arsenomolybdic acid are fractionally extracted with <I>n</I>-butanol: chloroform (1 : 3) and <I>n</I>-butanol : ethyl acetate (1 : 1), respectively. The effects of silicic acid and germanic acid are removed by regulating the concentration of nitric acid during the extraction. The concentration of reducing agent to be added in the extracted solvent layer and its acidity have been investigated and a comparatively stable molybdenum blue has been obtained. Since this method is practically not influenced by the presence of many elements, a trace of phosphorus and arsenic can be extracted directly from the solution containing a large amount of copper, and a rapid and accurate colorimetric estimation is possible to the minimum of 0. 0001 %.
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