ネスラー試薬によるアンモニウムイオンの重量分析

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The brownish precipitate in Nesslers reaction was used for the gravimetric determination of ammonium ion in an aqueous solution. The composition of the precipitate is NHg2I, and the gravimetric factor of nitrogen is very small (0.02584). The recommended procedure are followings; The two-fold equivalent amount of Nesslers reagent (HgI42- : 2×10-2F, OH- : 4×10-1F ) is added slowly to 25 ml of sample solution. It is allowed to stand for at least ten hours at room temperature and then warmed for three hours on steam bath. The digested precipitate is filtered through a fine-pored glass filter (average pore size : 1 μ), washed by deionized water and dried at 150°C in air. Ammonium ion ranging from 2 to 4 mg as nitrogen in 25 ml of ammonium chloride solution was determined within error of 2.1% and standard deviation of 6.8%. Negative errors were observed for the lower contents of the ion, and also significant positive errors for the higher contents. The recognized interfering substances are comlexing agents such as potassium cyanide, potassium thiocyanide, ethylenediamine and pyridine, and reducing agents such as hydroxylamine hydrochloride and hydrazine hydrochloride.
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