EDTA滴定法测定铜镁中间合金中镁

铜镁合金是铜合金材料中具有代表性的高强高导合金,在电子通讯、交通运输等领域具有广泛的运用,冶炼中通常以中间合金形式添加镁,但对于铜镁中间合金中高含量镁鲜有准确测定方法。实验采用盐酸和硝酸混合酸溶解,再以六次甲基四胺溶液和铜试剂为沉淀剂,两步沉淀分离基体元素及杂质元素,残留的痕量金属离子采用L-半胱氨酸、三乙醇胺和盐酸羟胺溶液掩蔽,再用氨水-氯化铵缓冲溶液调节溶液pH值约为10,以铬黑T为指示剂,用EDTA滴定法测定铜镁中间合金中镁。通过条件实验确认了沉淀剂及掩蔽剂的加入量。按照实验方法测定铜镁中间合金实际样品中镁,测定结果的相对标准偏差(RSD,n=11)为0.27%~0.48%,加标回收率为99.6%~100.9%。方法满足金属镁质量分数为10%~30%的铜镁中间合金的检测要求。

Determination of magnesium in copper-magnesium master alloy by EDTA titration

Copper-magnesium master alloy is a kind of representative high-strength and high-conductivity alloy in copper alloy materials. It has been widely used in many fields such as electrommunication and transportation. Magnesium is usually added in smelting in the form of master alloy. However, there are few methods for the accurate determination of high-content magnesium in copper-magnesium master alloy. In experiments, the copper-magnesium master alloy sample was dissolved with hydrochloric acid-nitric acid mixture. Hexamethylenetetramine solution and copper reagent were used as precipitator to separate matrix elements and impurity elements via two-step precipitation. The residual trace metal ions were masked with L-cysteine, triethanolamine and hydroxylamine hydrochloride solution. Then the pH of solution was adjusted to about 10 using ammonia water-ammonium chloride buffer solution. The content of magnesium in copper-magnesium master alloy was determined by EDTA titration using chrome black T as the indicator. The addition amount of precipitator and masking reagent were obtained through conditional experiments. The content of magnesium in copper-magnesium master alloy sample was determined according to the experimental method. The relative standard deviations (RSD, n=11) of determination results were between 0.27% and 0.48%. The recoveries were between 99.6% and 100.9%. The proposed method could meet the detection requirements of copper-magnesium master alloy with mass fraction of magnesium in range of 10%-30%.