络合滴定法测定球墨铸铁脱氧剂中钙镁钡

根据球墨铸铁脱氧剂的特性,以硝酸-氢氟酸分解试样,采用高氯酸除去样品中的硅,以氨-氯化铵-过氧化氢-铜试剂沉淀分离稀土、锰、铁和钛等干扰元素后,用EDTA、DCTA络合滴定法分别测定样品中的钙、钙钡合量及镁元素含量,用差减法求得钡元素的含量。讨论了溶样方法、指示剂选择、杂质元素的干扰情况及其消除方法,确定了最佳实验条件。采用本方法对与球墨铸铁脱氧剂成分相似的稀土中间合金标准样品中的钙、镁、钡实验进行多次平行测定,测定值与认定值相符,测定结果的相对标准偏差(RSD ,n=5)为1.2%~3.6%。

Determination of calcium, magnesium and barium in ductile iron deoxidizer by complexometric titration

Based on the properties of ductile iron deoxidizer, the sample was decomposed by nitric acid-hydrofluoric acid. Silicon in sample was removed with perchloric acid. The interference elements such as rare earths, manganese, iron and titanium were precipitated and separated by ammonia-ammonium chloride-hydrogen peroxide-copper reagent. Subsequently, the content of calcium, aggregate content of calcium and barium and the content of magnesium in sample was determined by EDTA and DCTA complexometry, respectively, and the content of barium was obtained by subtraction method. The sample dissolution method, the selection of indicator, the interference and elimination method of impurities were discussed to obtain the optimal experimental conditions. The proposed method was applied to parallel determination of calcium, magnesium and barium in rare earth intermediate alloy certified reference materials which have similar component with ductile iron deoxidizer. The results were consistent with the certified values. The relative standard deviation (RSD, n=5) was 1.2 %-3.6 %.