硫氰酸盐分光光度法测定镍基合金中钨

应用硫氰酸盐分光光度法测定镍基合金试样中钨时,存在镍基合金较难溶解的问题,同时样品中较高含量的镍会干扰钨的测定。实验采用硝酸-氢氟酸混合酸溶解试样,通过加入氢氧化钠使其与基体镍反应生成氢氧化镍沉淀的方法实现了镍与钨的分离,然后用氯化亚锡作还原剂,在盐酸介质中,将钨被还原为钨(Ⅴ)与硫氰酸盐形成黄色配合物,建立了硫氰酸盐分光光度法测定镍基合金中钨的方法。实验表明,显色液中钨的质量浓度在0.096~19.24μg/mL范围内符合比尔定律,相关系数R~2=0.999 6。方法的检出限为0.025%,测定下限为0.084%。将实验方法用于测定两个镍基合金样品中钨,结果的相对标准偏差(RSD,n=6)小于0.50%。按照实验方法测定6个镍基合金样品中钨,结果与电感耦合等离子体原子发射光谱法(ICP-AES)测定结果相一致。

Determination of tungsten in nickel base alloy by thiocyanate spectrophotometry

In the determination of tungsten in nickel base alloy by thiocyanate spectrophotometry, the high content of nickel would interfere with tungsten as nickel base alloy are usually difficult to dissolve. The samples were dissolved by the mixture of nitric acid-hydrofluoric acid, and nickel was separated from tungsten through producing nickelous hydroxide from nickel and sodium hydroxide. With stannous chloride as reductant, tungsten was reduced into yellow complex of tungsten and thiocyanate in the medium of hydrochloric acid. Thus, a thiocyanate spectrophotometric analysis of tungsten in nickel base alloy was established. The selection of the sample decomposition method and the method of eliminating the interference of the matrix element nickel were analyzed and discussed. The results showed that, Beer’s law was obeyed for tungsten within the range of 0.096-19.24 μg/mL, with the correlation coefficient of R²=0.999 6. The detection limit was 0.025%, while the low limit of determination was 0.084%. The proposed method had been applied to determine tungsten in two nickel base alloy. The relative standard deviation was (RSD,n=8) was less than 0.50%. The results of tungsten in six nickel base alloy samples were consistent with those of inductively coupled plasma atomic emission spectrometry(ICP-AES).