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近年不同作者用4-(2’-噻唑偶氮)间苯二酚(TAR)于分析工作。本文作者等实验确定,在乙酸—乙酸铵锾冲介质中此试剂遇铌形成红紫色络合物,可用于铌的分光光度测定。适宜的显色pH值为5.00—5.75。络合物吸收峯位于近545毫微米处,克分子消光系数为3.22·10~4。用等吸收点法、改进的斜率比法及其他不同方法确定铌与TAR的络合比为1:1。在pH 5.60用不同方法测定络合物的表观稳定常数值为:连续变更浓度法2.42·10~5;平衡移动法3.63·10~5;Клейнер计算法3.05·10~5。在室温时反应速度较缓慢。用分
In recent years, different authors used 4- (2’-thiazolylazo) resorcinol (TAR) for analysis. The authors et al. Determined that this reagent forms a magenta complex with niobium in acetic acid-ammonium acetate buffer and can be used for the spectrophotometric determination of niobium. Appropriate color development pH is 5.00-5.75. The complex absorption peak is located at 545 nm and the molar extinction coefficient is 3.22 · 10 ~ 4. The ratio of niobium to TAR was determined to be 1: 1 using equal absorption point method, modified slope ratio method and other different methods. The apparent stability constants of complexes determined by different methods at pH 5.60 are: 2.42 · 10-5 by continuous concentration change method, 3.63-10-5 by equilibrium shift method, and 3.05-10-5 by the calculation method of Клейнер. The reaction rate is slower at room temperature. Use points