亜硫酸への酸化によるシアンイオンの定量(ノート)

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It has been found that cyanide in an alkaline solution is quantitatively oxidized to nitrite by hypochlorite in the presence of potassium bromide, and the nitrite produced is determined spectrophotometrically with sulfanilamide and N-1-naphthylethylenediamine reagents. It was applied to a determination of cyanide, and the conditions for determination were investigated. The procedure established is as follows. To 20ml of a sample solution are added 1ml of 0.5M sodium hydroxide solution, 2ml of 0.75% potassium bromide solution and 1ml of sodium hypochlorite solution cotaining 0.2% active chlorine. The solution is allowed to stand for 6hrs. in boiling water, and transferred to a 50ml volumetric flask after cooling. By adding 1ml of 4% arsenic trioxide in 1M sodium hydroxide to the solution, the excess hypochlorite is completely decomposed. Two milliliters of 1% sulfanilamide in 1.2M hydrochloric acid and then, after 28min, 1ml of 0.1% N-1-naphthylethylenediamine solution are added and the whole is diluted to the mark with water. After 10min, the absorbance is measured at 543mμ with a 1-cm cell against the reagent blank. The sensitivity of this method is onehalf of the pyridine-pyrazolone method.
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