銅中の微量水銀の吸光光度定量

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タイトル別名
  • Spectrophotometric determination of small amounts of mercury in copper
  • ドウ チュウ ノ ビリョウ スイギン ノ キュウコウ コウド テイリョウ

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A spectrophotometric method for the determination of small amounts of mercury in pure copper has been presented. A small amount of mercury is selectively extracted as mercury-diethyldithiocarbamate complex from an alkaline aqueous solution containing large amounts of copper and EDTA into toluene and is backextracted from the organic layer into a 0.7N nitric acid aqueous solution containing 0.0075M potassium iodide, 0.005M potassium bromate and 0.025M potassium bromide (backextraction solution). Then Crystal Violet colorimetric method is carried out for the determination of mercury in the backextraction solution. The recommended procedure is as follows:<BR>Two grams of sample was gently dissolved in nitric acid (1+1) solution. The pH was ajdusted to 8.09.0 with ammonia after an addition of 40ml of 1M EDTA solution. It was transferred into a separatory funnel, and 5.0ml of 0.1% sodium-diethyldithiocarbamate solution was added. The solution was shaken vigorously with 5ml of toluene for 5min and the aqueous layer was discarded. Ten ml of the backextraction solution was added into the separatory funnel and the mixture was shaken vigorously for 5min and the aqueous layer was transferred into another separatory funnel. Five drops of 20% sodium metabisulphite solution was added in order to reduce the free iodine, then 0.4ml of 1.0% Crystal Violet solution was added and the solution was immediately shaken with 5ml of toluene for 10sec. The amount of mercury was determined from the absorbance of the toluene layer at 605nm within 3min after the extraction.<BR>In case of the presence of copper and EDTA, many elements such as Pb, Zn, Bi, Ni, Co, Sn and Sb are not extracted as DDC complexes into the organic layer. Not more than 0.5mg of silver, 0.1mg of thallium and 5μg of gold do not interfere. Silver at high concentration interferes the first separation by extraction of mercury as DDC complex from the solution containing copper and EDTA. More than 10μg of gold interferes seriously but gold are selectively removed from the toluene layer containing DDC complexes by washing with 0.5N nitric acid solution. In this case, mercury and copper are not removed into the aqueous solution.<BR>The mercury content in some vacuum melt copper and oxygen free highpurity copper was determined to be less than 0.25ppm.

収録刊行物

  • 分析化学

    分析化学 21 (7), 925-929, 1972

    公益社団法人 日本分析化学会

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