Spectrophotometric determination of ferro- and ferricyanide ions with 1, 10-phenanthroline

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  • １，１０‐フェナントロリンによるフェロシアン化物イオンおよびフェリシアン化物イオンの吸光光度定量
  • 1 10 フェナントロリン ニヨル フェロシアンカブツ イオン オヨビ フェリ
  • 1,10-フェナントロリンによるフェロシアン化物イオン及びフェリシアン化物イオンの吸光光度定量

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Abstract

The spectrophotometric determination methods of ferrocyanide in the form of prussian blue or the ferricyanide ion with manganese(III) are not sensitive. The pyridine-benzidine, pyridine-pyrazolone, or mercuric thiocyanate methods applied to hydrogen cyanide after isolation by distillation are time-consuming. When the stability constant of ferrocyanide ion (log β6=24 or 36.9) is compared with that of ferroin. ion (log β3=21.3, logK1=5, and log K3=9.85), it is reasonable to expect that ferrocyanide ion could be converted into ferroin ion in the presence of a large excess of 1, 10-phenanthroline. However, the reaction proceeds very slowly. In order to accelerate the reaction, heating, irradiation of ultraviolet rays, and addition of mercuric ion, mercurous ion, or mercury were examined. Heating in the presence of mercuric ion gave the best result. Ferricyanide ion could be decomposed more easily by the same method. The following procedure is recommended. Transfer an aliquot of the sample solution (containing not more than 200μg of ferrocyanide ion) to a small eggplant type flask. Add 1 ml of 1% ascorbic acid, 2 ml of 0.5 M 1, 10-phenanthroline in 1 M acetic acid, and 0.5 ml of 10-3 M mercuric chloride. Adjust the pH of the solution to 24 with diluted sodium hydroxide or sulfuric acid, and heat in a boiling water bath for 20 min. Transfer the solution to a 10 ml volumetric flask, and dilute to the mark with water. Measure the absorbance at 510 nm using reagent blank as the reference. Ferricyanide ion can be determined by the same procedure, except the heating time of 10 min instead of 20 min. The calibration curve is prepared using the solution of Mohr's salt by the same procedure without heating. The proposed method is simple and sensitive, and is useful for the determination of ferro- and ferricyanide ions, either or both, in waste water.

Journal

  • BUNSEKI KAGAKU

    BUNSEKI KAGAKU 24 (11), 677-681, 1975

    The Japan Society for Analytical Chemistry

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