EDTA滴定法测定除尘灰中锌含量

采用灰化后再溶解试样的方法,成功解决了除尘灰因碳含量过高而难于溶解的问题;将灰化后的试样以HCl-HNO3-HF-HClO4混酸溶解,在氯酸钾存在下,以铁盐作载体,用氨水沉淀分离大部分铁、铝、铅等元素,以硫脲-氟化物、硫代硫酸钠、抗坏血酸作掩蔽剂,掩蔽剩余少量铜、锡、铁等干扰元素,在pH=5.5~6条件下,以二甲酚橙为指示剂,用EDTA标准溶液滴定得到锌的含量。方法的相对标准偏差在0.75%~2.8%,加标回收率在98.0%~102%。方法操作简便,且分析结果准确度、重现性较好,可以满足生产检验的需要。

Determination of Zinc Content in Dust by EDTA Titration Method

By using sample ashing method together with sample dissolution method, the problem that the dust is difficult to be dissolved because of high carbon content in the dust has been solved. The ashed samples were dissolved by the mixed acids of hydrochloric acid, nitric acid, hydrofluoric acid and perchloric acid. In the presence of potassium chlorate, iron salts being used as the carriers, most of iron, aluminum, lead were separated by ammonia. Thiourea - fluoride, sodium thiosulfate and ascorbic acid were used as masking agents to mask the remaining small amount of copper, tin, iron and other interfering elements.Under the condition of pH 5.5 to 6, zinc was titrated by EDTA standard solution when xylenol orange was as indicator. The relative standard deviation and standard recovery rate of the method was 0.75% to 2.8% and 98.00% to 102.0%, respectively. This method is simple. By this method, analytical results are accurate and repeatability is good, which can meet the needs for manufacturing inspection.