The conditions for color reaction of 4-(2-pyridineazo)-resorcinol (PAR) with niobium was investigated, and a method for the determination of niobium in acid sludge (which was expressed as niobium pentoxide) by spectrophotometry was developed. The results showed that in the solution at pH 5. 6-6. 0, a red ternary complex was formed by PAR with the complex anion of niobium tartrate in the presence of beryllium salt and tartaric acid, and its maximum absorption wavelength was 550 nm with apparent molar absorptivity (ε) of 2. 6×104 L · mol-1 · cm-1. Under the optimum experimental conditions, there was a good linear relationship between the niobium pentoxide concentration within the range of 0. 02 to 0. 8 μg/mL and its corresponding absorbance, the correlation coefficient (r) was 0. 998 8 and the detection limit was 0. 004 8 μg/mL. The method was used for the determination of niobium in acid sludge. The results were in accordance with those obtained by chlorosulphophenol S spectrophotometry, and the relative standard deviations were 2. l%-2. 5%.%研究了4-(2-吡啶偶氮)间苯二酚(PAR)与铌的显色条件,建立了测定酸泥中铌(以五氧化二铌来表示)含量的分光光度法.结果表明,在pH5.6～6.0的溶液中,在铍盐和酒石酸存在下,PAR与酒石酸铌的络阴离子形成红色三元络合物.该络合物最大吸收波长为550nm,表观摩尔吸光系数ε=2.6×104 L·mol-1·cm-1,在最佳实验条件下,五氧化二铌的浓度与其对应的吸光度在0.02～0.8 μg/mL范围内呈良好的线性关系,相关系数r=0.998 8,检出限为0.004 8μg/mL.方法用于酸泥中铌的测定,结果与氯代磺酚S光度法一致,相对标准偏差为2.1％～2.5％.
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