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提出用[BF_4]~-作释放剂,选择性螫合滴定法测定试样中的铝含量。方法基于加入过量的CDTA(环己二胺四乙酸),螯合Al~(3+)和其它金属离子。然后以5-Br-PADAP-乳化剂OP-Tween 80为混合指示剂,在pH 5～6时用CuSO_4标准溶液返滴过剩的CDTA。加入[BE_4]~-溶液置换释放Al-CDTA螯合物中的CDTA,释放出的CDTA再用CuSO_4标准溶液滴定,从而计算出铝含量。实验研究了各种阴阳离子的干扰影响,结果表明大量离子(包括Sn~(4+)、Ti~(4+)、Zr~(4+))完全不干扰。滴定终点变化十分敏锐、清晰,操作简便,结果准确。已成功地应用于测定矾土、钢渣、铝镁合金和土壤中的铝,结果满意。
Proposed [BF_4] ~ - as a release agent, combined with the selective determination of aluminum content in the sample titration. The method is based on the addition of excess CDTA (cyclohexanediaminetetraacetic acid) to chelate Al 3+ and other metal ions. Then 5-Br-PADAP-emulsifier OP-Tween 80 as a mixed indicator, at pH 5-6 with CuSO 4 standard solution of excess CDTA. The addition of [BE_4] ~ - solution displaces CDTA in the Al-CDTA chelate, and the released CDTA is titrated with CuSO_4 standard solution to calculate the aluminum content. The interference effects of various anions and cations are experimentally studied. The results show that a large number of ions (including Sn 4+, Ti 4+ and Zr 4+) do not interfere at all. Titration endpoint change is very sharp, clear, easy to operate, the result is accurate. Has been successfully applied to the determination of bauxite, steel slag, aluminum-magnesium alloy and soil aluminum, with satisfactory results.