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测定水中微量铬,首先要将水中低价铬氧化成六价铬。据有关资料报导,常用下列两种氧化方法:(1)在碱性溶液中用高锰酸钾氧化,剩余的高锰酸钾用乙醇还原,然后过滤除去二氧化锰。此法不仅操作较繁,而且易造成铬离子的损失。(2)在酸性溶液中用高锰酸钾氧化,剩余的高锰酸钾用叠氮化钠(NaN_3)或亚硝酸钠还原。此法所用的叠氮化钠量如果控制不合适,结果再现性差;用亚硝酸钠还原,剩余的亚硝酸钠一定要用尿素分解完全,否则会使结果偏低。本文提出在较广泛的酸、碱性范围内,用高锰酸钾将水样中的低价铬离子氧化为六价
Determination of trace chromium in water, the first low-cost chromium oxidation of water into hexavalent chromium. According to the information reported, the following two oxidation methods are commonly used: (1) oxidation with potassium permanganate in an alkaline solution, reduction of the remaining potassium permanganate with ethanol, and filtration to remove the manganese dioxide. This method not only more complicated operation, but also easily lead to the loss of chromium ions. (2) Oxidation with potassium permanganate in acidic solution, with the remaining potassium permanganate reduced with sodium azide (NaN 3) or sodium nitrite. If the amount of sodium azide used in this method is not suitable for control, the reproducibility is poor; with sodium nitrite reduction, the remaining sodium nitrite must be completely decomposed with urea, otherwise the result will be low. In this paper, it is proposed that potassium permanganate is used to oxidize low-valent chromium ions in water samples to hexavalent