EDTA滴定法测定镍镁合金中镍和镁

建立了EDTA络合滴定法测定镍镁合金中镍和镁含量的分析方法。试样以硝酸、滴加盐酸溶解,分取一定体积的试液,加柠檬酸掩蔽铁离子,以丁二酮肟沉淀镍,用硝酸和高氯酸破坏沉淀剂,以紫脲酸铵作指示剂,用EDTA标准溶液滴定镍含量;同时,另取部分试液,以铜试剂预先分离镍基体,并以盐酸羟胺、氰化钾、三乙醇胺等掩蔽剩余干扰离子,以铬黑T为指示剂,用EDTA标准溶液滴定镁含量。对沉淀剂进行探讨,结果表明,测定镍时,加沉淀剂丁二酮肟与其络合沉淀,选择性好;而测定镁时,选择铜试剂络合沉淀基体镍和其他干扰离子,滤液可直接用于镁离子的测定,干扰少。对镍镁合金样品中镍、镁含量进行多次平行测定,相对标准偏差(RSD,n=6)分别为0.23%~0.57%和0.76%~0.90%。并模拟镍镁合金的主要成分及含量合成试样溶液进行测定,结果与理论值一致。将方法应用于镍镁合金实际样品分析,结果与参照方法结果一致。

Determination of nickel and magnesium in nickel-magnesium alloy by EDTA titrimetry

The analysis method of nickel and magnesium contents in nickel-magnesium alloy by EDTA complexometric titration was established. The sample was dissolved with nitric acid and hydrochloric acid. A certain volume of solution was sampled to precipitate nickel with dimethylglyoxime by adding citric acid to mask the iron ions. Then, the precipitating agent was destroyed by nitric acid and perchloric acid. The content of nickel was titrated with EDTA standard solution using murexide as indicator. Meanwhile, a certain volume of solution was sampled to pre-separate nickel matrix with cuprisone. The residual interference ions were masked by adding hydroxylamine hydrochloride, potassium cyanide and triethanolamine. The content of magnesium was determined with EDTA standard solution using chrome black T as indicator. The precipitating agent was discussed. The results showed that the addition of dimethylglyoxime for complex-precipitation of nickel exhibited good selectivity. During the determination of magnesium, the cuprisone was selected to precipitate nickel matrix and other interference ions. The content of magnesium ions in filtrate could be directly determined with little interference. The content of nickel and magnesium in nickel-magnesium alloy sample was determined for several times. The relative standard deviation (RSD, n=6) was 0.23%-0.57% and 0.76%-0.90%, respectively. The main components and content in nickel-magnesium alloy was simulated to synthesize sample solution for determination. The found results were consistent with the theoretical values. The proposed method was applied to the analysis of actual nickel-magnesium alloy sample, and the determination results were consistent with the reference method.