铜合金中铝和铁顺序示波滴定

SUCCESSIVE OSCILLOPOLAROGRAPHIC TITRATION OF ALUMINUM AND IRON IN COPPER ALLOYS

叙述了用示波滴定法连续测定铜合金中铝、铁。试样酸溶后 ,在 pH 5 .5的HOAc NH4 OAc缓冲介质中 ,用Zn2 +标准溶液顺序示波滴定NH4 F置换Al EDTA和KCl、KF置换Fe EDTA中的EDTA ,间接计算出铝和铁的含量。该方法快速简便 ,终点直观 ,准确度、精密度均较高。标准加入回收率在 99.0 % 10 0 .4 %之间 ,RSD <0 .5 %。

Oscillopolarographic titration was applied to the determination of Al and Fe in copper alloys. An excess of EDTA solution was added to the sample solution buffered at pH 5.5 with NH 4OAc HOAc solution to complex all the metal ions which can react with EDTA under the specified condition. After the un reacted EDTA was titrated with Zn 2+ standard solution (0.02mol·L -1 ) as shown by the appearance of an incision of Zn 2+ ion, the Al(Ⅲ) and Fe(Ⅲ) contents were then determined by titration again with the Zn(Ⅱ) standard solution in two successive steps. In the 1st step, NH 4F was added to liberate an eqivalent amount of EDTA from the Al EDTA complex, which was titrated with Zn 2+ standard solution ( V 1). In the 2nd step, KCl and KF were added to liberate an eqivalent amount of EDTA from the Fe EDTA complex, which was titrated with Zn 2+ standard solution ( V 2) again. The contents of Al and Fe of the sample were calculated by V 1 and V 2 respectively. RSD′s obtained were less than 0.5% and the recoveries were in the range of 99.0% to 100.4%.