シアンイオンの微量銀滴定におけるNAS 11-18電極の利用

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Sodium ion selective glass electrode has been employed as an end-point detector in the automatic microtitration of cyanide ion with silver ion. An aliquot volume of 0.005M potassium cyanide standard solution containing 0.01M potassium hydroxide was accurately pipetted into a 50ml beaker. The pH of the solution was adjusted to 10.5 by adding 5ml of potassium carbonate-potassium bicarbonate buffer and was finally made up to 50ml with distilled water. Automatic titration was then carried out with 0.005M silver nitrate standard solution at a delivery speed of 0.5ml/min by using a sodium ion selective glass electrode(Corning NAS 11-18) and a double-junction SCE. Two potential jumps were observed for the formation of dicymosilver complex and of silver cyanide precipitate. The first potential jump was much smaller than the second one but it was sharp and was easily recognized on the recorder chart so that this inflection point can be used as an end point. The cyanide standard solution is stable for a few days in a polyethylene bottle. However, when the sample solution was delivered into a 100 ml beaker, cyanide ion was decomposed in air at a rate of 1% of the initial concentration during 10 min. In a 50 ml beaker, on the other hand, the stability was improved because the exposed area of the solution to air was reduced. The reproducible end-point was then obtained when the titration was carried out within 10 min. The statistic study of the reproducibility yielded 8(μl) as the standard deviation against 2.500 ml of the titrant.
社団法人日本分析化学会の論文
1977-06-05

シアンイオンの微量銀滴定におけるNAS 11-18電極の利用

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