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应用络合滴定法测定铜合金中铝的关键是如何分离干扰元素。常用的有铜试剂分离、氢氧化钠分离、电解分离后用氟化钠析出等等。这些分离方法不仅手续繁杂,而且也不能将所有的干扰元素分离除去,特别是对含锡的铜合金,采用硝酸分解并蒸干的方法,正如有的文献所指出的[理化检验,(1),29(1973)],在硝酸溶液中形成的偏锡酸沉淀会吸附部分铝,使铝受到损失,并易为人们所忽略。为克服锡的干扰,试样经盐酸、过氧化氢分解后,用高氯酸冒烟,使偏锡酸沉淀完全,并且不吸附铝。经多次试验,高氯酸冒烟时间为1—5分钟,测得数据不变。高氯酸的加入量以4毫升最佳。所获结果令人满意,很有实用价值。
The key to determination of aluminum in copper alloy by complexometric titration is how to separate the interfering elements. Commonly used copper reagent separation, sodium hydroxide separation, electrolysis after precipitation with sodium fluoride and so on. These separation methods are not only complicated procedures, but also can not separate all the interference elements removed, especially for tin-containing copper alloy, nitric acid decomposition and evaporated to dry, as pointed out in some literature [physical and chemical testing, (1) , 29 (1973)], metatitanic acid precipitate formed in nitric acid solution will adsorb part of the aluminum, the loss of aluminum, and easily overlooked. To overcome the interference tin, the sample by hydrochloric acid, hydrogen peroxide decomposition, smoking with perchloric acid, the partial stannic acid precipitation completely, and does not adsorb aluminum. After many tests, perchloric acid smoke for 1-5 minutes, the measured data unchanged. The amount of perchloric acid to 4 ml best. The results obtained are satisfactory and of great practical value.