A new method was introduced to determine alumina in ores by sodium diethyldithiocarbamate seperation-EDTA titration. The manganese ore swatch was melt with NaOH, Na3PO4 and Na2O2 mix melting agent, the interference of Ca, Mg, Ti was eliminated, lixiviated with hot water containing anhydrous ethanol, Mn in sample was precipitated out as MnO2. The solution was dryly filtered, prepared into solution in a definite volume. The filtrate was neutralized to weak acidity, adding diethyl dithio amino formic acid sodium in it, some metal cations were separated by forming complex which were difficult to dissolve in water. After repeated filtration, a part of filtrate was reacted with excess EDTA standard solution, the rest EDTA was titrated with zinc standard solution, and then the content of alumina was gotten. This method adopts two xylenol orange as the indicator, meanwhile, adding a small amount of cetylpyridinium chloride, color mutation was more sensitive at the end point of titration. The method could improve the detection accuracy, and easy to master. The relative standard deviations of the sample determination value were 0.42%-1.08%(n=5), and the recoveries of the standard addition sample were 97.39%-99.94%. This method only requires once titration, and need not to use the solution containing lead, copper and fluoride, and it is convenient and environmentally friendly.%介绍一种利用二乙基二硫代氨基甲酸钠分离后以EDTA滴定测定矿石中铝的新方法.锰矿样品用NaOH,Na3PO4和Na2O2混合熔剂熔融,消除Ca,Mg,Ti的干扰,用含无水乙醇的热水浸取,其中的Mn变为MnO2沉淀析出,干过滤,定容.将滤液中和至弱酸性,加入二乙基二硫代氨基甲酸钠,一些金属阳离子形成难溶水的络合物而分离,再次过滤,一定量的滤液与过量的EDTA标准溶液反应,用锌标准溶液滴定剩余的EDTA,即得氧化铝的含量.该法采用二甲酚橙为指示剂,同时加入少量氯化十六烷基吡啶,滴定终点颜色突变明显,改善了测量精密度,操作易于掌握.样品测定结果的相对标准偏差为0.42%~1.08%(n=5),加标回收率为97.39%~99.94%.分析过程只需滴定一次,且不使用含铅、铜、氟溶液,方法便捷环保.
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