以1M醋酸——醋酸铵缓冲液(pH 5.8)为底液,在土壤待测液中加入过量的EDTA,用锌盐回滴过量的EDTA,再加入氟化铵,用锌盐滴定释放出来的EDTA。利用Zn~(2+)在示波极谱图上切口的出现指示终点。土壤样品分析结果表明,此法较二甲酚橙指示剂法终点直观敏锐,精密度符合常量分析的要求,且可定量回收。 To 1 M acetic acid - ammonium acetate buffer (pH 5.8) as the base solution, the soil to be measured solution was added excess EDTA, zinc salt with excess EDTA back, then add ammonium fluoride, titration with zinc release EDTA. The use of Zn ~ (2+) in oscillopolarography incision on the appearance of the end point. The result of soil sample analysis shows that this method is more intuitive and sharp than the endpoint of xylenol orange indicator, and the precision accords with the requirement of constant analysis and can be recovered quantitatively.