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本文合成了新显色剂2-(5-溴-2-噻唑偶氮)-5-二乙氨基苯甲酸(简称5-Br-TAEB),利用光度法测定了试剂的三级质子化常数,研究了它与镍显色反应的最佳条件,同时对表面活性剂及无机盐的作用机理进行了初步探讨。实验结果表明,在NaCl和NaDS存在下,pH=5.0～8.0范围内,5-Br-TAEB与镍形成稳定的蓝色络合物,络合比为Ni~(2+):5-Br-TAEB=1:2,摩尔吸光系数ε_(642)=1.23×10~5 SL·mol~(-1)·cm~(-1)。镍浓度在0～10μg/25ml范围内服从比尔定律,方法用于铝合金中镍的测定,结果满意。
The new reagent 2- (5-bromo-2-thiazolylazo) -5-diethylaminobenzoic acid (referred to as 5-Br-TAEB) was synthesized in this paper. The tertiary protonation constants of the reagent were determined by spectrophotometry. The optimum conditions for its color reaction with nickel were studied. At the same time, the mechanism of action of surfactants and inorganic salts was discussed. The experimental results show that 5-Br-TAEB forms a stable blue complex with nickel in the presence of NaCl and NaDS at a pH range of 5.0-8.0, with a complex ratio of Ni 2+: 5-Br- TAEB = 1: 2, molar extinction coefficient ε 644 = 1.23 × 10 5 SL · mol -1 cm -1. The Beer’s law was obeyed in the range of 0 ~ 10μg / 25ml for nickel concentration. The method was applied to the determination of nickel in aluminum alloy with satisfactory results.