Spectrophotometric determination of the micro amounts of iodide and bromide by the formation of triiodide ion.

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Other Title
  • 三よう化物イオンの生成を利用する微量よう化物及び臭化物イオンの吸光光度定量
  • 3 ヨウカブツ イオン ノ セイセイ オ リヨウスル ビリョウ ヨウカブツ オ
  • 三ヨウ化物イオンの生成を利用する微量ヨウ化物及び臭化物イオンの吸光光度定量

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Description

Iodide ion is oxidized to iodine with hydrogen peroxide in sulfuric acid solution. Bromide and iodide ions are oxidized to bromine and iodate ion with potassium permanganate in sulfuric acid solution. Iodine or bromine in carbon tetrachloride is quantitatively converted into triiodide ions in aqueous phase by the back-extraction with an excess of potassium iodide solution. The analytical procedure for iodide ion is as follows. To 10 ml of a sample solution containing iodide ion up to 10 ppm in a separatory funnel, 1 ml of 4.5 M sulfuric acid and 1 ml of 3 % hydrogen peroxide are added. After standing for 5 min, 5 ml of carbon tetrachloride is added to the funnel and it is shaken for 30 s. The carbon tetrachloride phase is transferred to the other funnel and 5 ml of 0.05 M sulfuric acid is added. The mixture is shaken for 30 s to wash the organic phase. Then, the organic phase is transferrd again to the other funnel and 10 ml of 0.5 M potassium iodide solution is added. The mixture is shaken for 30 s. The absorbance of the aqueous phase is measured at 350 nm with a quartz cell against water. For the determination of bromide ion, 1 ml of 3 M sulfuric acid and 1 ml of 0.015 M potassium permanganate are added to 10 ml of a sample solution containing bromide ion up to 10 ppm in a separatory funnel, and allowed to stand for 5 min. The subsequent procedure is the same as that for iodide ion described above, except for the washing of organic phase with 5 ml of 0.5 M sulfuric acid. The relative standard deviation for the determination of 63.3 ppm bromide ion in sea water sample was calculated to be 1.3 % for 10 repeated measurements.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 34 (2), 81-86, 1985

    The Japan Society for Analytical Chemistry

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