混合溶媒中の酸-塩基指示薬の動向(II)

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書誌事項

タイトル別名
  • The behavior of acid-base indicators in the mixed solvents(II)
  • コンゴウ ヨウバイ チュウ ノ サン-エンキ シジヤク ノ ドウコウ 2
  • Mixed indicators
  • 混合指示薬

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抄録

Ranges of color change of some pH indicators in the mixed solvents were determined by drawing their ideal pH-absorbance curves using the equation Y=2-log{(1-X)/X} as 0.01≤X≤0.99.<BR>Ranges of color change became generally narrower as the concentration of organic solvent increased, pH scale 2.08 (40%) thus diminishing to 1.87 (80%) in methanolic dimethyl yellow (D. Y.) solution and 1.72 (40%) to 1.66 (80%) in methanolic bromcresol green (B. C. G.) solution. Color change points of mixed indicators were obtained by overlapping the curves of any two component indicators, where the curves were corrected by color responsibility of naked eyes.<BR>The color change points of mixed indicators were moved by change in their mixing ratios. In some cases the selection of an appropriate mixing ratio enabled the color change on a disired pH adjacent to the usual color change point of mixed indicator. Thus, color change point 5.1 (Methyl Red : B. C. G. =1 : 3 usually) changed to 4.7 (1 : 6) and 3.3 (D. Y.: Methylene Blue =1 : 1 usually) changed to 2.7 (1 : 1.5).<BR>These new ratios were decided geometrically by overlapped curves. Good results were obtained in the automatic colorimetric titration by using filters of colored solution under the pH condition of the usual color change point in a water medium.

収録刊行物

  • 分析化学

    分析化学 13 (12), 1253-1258, 1964

    公益社団法人 日本分析化学会

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