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铜的碘量法测定为氧化剂的存在所干扰,因为它们也能自碘化钾中析出碘。测定矿石中的铜,干扰元素有Fe~(3+)、As~(5+)、As~(5+)、Sb~(5+)、Sb~(3+)及NO_3~-。其中硝酸根的干扰可以在矿样溶解后加热除尽,三价砷可以在矿样溶解时用硝酸氧化为五价。五价砷和锑只有在强酸溶液中才与碘化钾作用析出碘,因此,可以借控制酸度来消除它们的干扰。三价铁是碘量法测定铜的主要干扰元素,目前国内大多采用氟化物作掩蔽剂,使铁转变为不与碘化钾作用的铬离子(FeFe_6~(3-)),此法方便、准确。但流程中使用大量的氟化物,污染环境,有害人体。有人建议用焦磷酸钠代替氟化物,这时生成的铁的铬离子也不与碘化钾反应。但由于过量的焦磷酸钠
The copper iodometric method determines the presence of oxidants that interfere with their ability to precipitate iodine from potassium iodide. The determination of copper in the ore, interference elements Fe ~ (3 +), As ~ (5 +), As ~ (5 +), Sb ~ (5 +), Sb ~ (3+) and NO_3 ~ -. Among them, the interference of nitrate can be eliminated after the sample is dissolved, and the trivalent arsenic can be oxidized to pentavalent with nitric acid when the sample is dissolved. Pentavalent arsenic and antimony only precipitate iodine with potassium iodide only in a strong acid solution. Therefore, the acidity can be controlled to eliminate their interference. Ferric iron is the main interfering element in the determination of copper by iodometric method. At present, fluoride is used as a masking agent in most countries to convert iron to chromium (FeFe6 ~ (3-)) which is not bound to potassium iodide. This method is convenient and accurate. But the process uses a lot of fluoride, pollute the environment, harmful to the human body. It has been suggested that sodium pyrophosphate should be used instead of fluoride, and the resulting chromium ions do not react with potassium iodide. But due to excessive sodium pyrophosphate