耐尔蓝-钽钼杂多酸缔合物显色体系的研究

Study on the Colour Reaction of the Ion-Associate Complex of Nile-Blue and Molybdotantalate Heteropoly Acld

本文研究了耐尔蓝(NB)-钽钼杂多酸-聚乙烯醇高灵敏的显色体系。在0.013～0.13mol/L硫酸溶液中,钽与钼酸铵形成钽钼杂多酸,在聚乙烯醇存在下,在1.08～1.98mol/L硫酸介质中,钽钼杂多酸与耐尔蓝形成离子缔合物。缔合物的最大吸收在625nm,表观摩尔吸光系数ε值为2.26×10~6L·mol^(-1)·cm^(-1),Ta(Ⅴ)浓度在0～2.6μg/25mL符合比耳定律。用平衡移动法确定了缔合物的摩尔比为Ta(Ⅴ):NB=1:3。所提出的方法已用于合金钢和某些矿物中痕量钽的测定,结果较满意。

A highly sensitive colour reaction of Nile blue(NB) and molybdotantalate heteropoly acid has been studied. In 0. 013～0.13mol/L sulfuric acid solution,tantalum(V) and ammonium molybdate form the molybdotantalate heteropoly acid complex,then in 1.08～1.98mol/L sulfuric acid medium,the ion-associate complex of molybdotantalate heteropoly species and Nile-blue is formed in the presence of polyvinyl alcohol. The ion-associate exhibits a maximum absorptivity at 625nm,and its apparent molar absorptivity was found to be 2.26×10~6L·mol^(-1)·cm^(-1). Beer's law is obeyed in the range of 0 to 2.6μg/ mL Ta(V). The molar ratio of Ta(V) to NB in the ion-associate was established to be 1:3 by equilibrium movement method. The proposed method has been used for the determination of trace tantalum (V) in steels and some ores with satisfactory results.