<研究>黄血鹽に依る亞鉛の定量(第1報) : 滴定の精度並にアルカリ鹽の影響に就いて

概要

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When zinc sulfate solution was titrated directly with potassium ferrocyanide either at 60℃ or at room temperature, using diphenylamine as an indicator, color change of the indicator could not be recognized at equivalent point. Addition of ammonium chloride made the color change distinct, but errors observed were great. Presence of an excess of potassium ferrocyanide is favourable for the completion of zinc potassium ferrocyanide. Excellent results were obtained, therefore, when a small excess of the former was added in one stroke, and after the double salt was completed on mixing, the excess was titrated with proper reagent such as zinc sulfate or potassium dichromate solution. About 5 mg of potassium ferricyanide was added to 100 ml of solution and the acidity was adjusted to about 1 N with sulfuric acid. Sodium sulfate had no effect on the titration of zinc. In the presence of as much as 5〜20 g of the former in 100 ml, good results were obtained. Errors caused by sodium chloride and sodium nitrate were relatively small. Effects of ammonium and potassium salts were great. Addition of 10 g of ammonium chloride caused the error amounting to 5%. Presence of these salts made color change of the indicator sharp. In their absence, it was necessary to titrate slowly near the equivalent point. Amounts of diphenylamine used had no effect on the titration.
東北大学の論文
1951-03-25