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在SLS等表面活性剂存在下,钴(Ⅱ)与新显色剂2-(5-溴-2-噻唑偶氮)-5-二乙氨基苯酚(5-Br-TADAP)在pH6—9时形成紫红色电中性的胶束增溶络合物。钴在络合物中以钴(Ⅱ)形式存在,Co(Ⅱ):5-Br-TADAP=1∶2,其表观稳定常数为3.5×10~(11)(20℃,μ=0.1)。据此确定了Co(Ⅱ)-5-Br-TADAP络合物的结构。该络合物的λ_(max)为590nm,ε_(590)为8.24×10~4L·mol~(-1)·cm~(-1)。Co(Ⅱ)-5-Br-TADAP络合物一旦形成后,加入的EDTA不再能将其分解,但能分解许多其他金属离子与试剂形成的络合物。在25毫升体积中,钴量在0—20微克范围内遵守比耳定律。本法简便、快速、准确可靠,将其用于低合金钢中小量或痕量钴的测定,取得了满意的结果。
In the presence of surfactants such as SLS, cobalt (Ⅱ) and the new chromogenic reagent 2- (5-Br-TADAP) A magenta neutralized micellar solubilization complex was formed. Co (Ⅱ): 5-Br-TADAP = 1: 2, the apparent stability constant is 3.5 × 10-11 (20 ℃, μ = 0.1) . The structure of Co (Ⅱ) -5-Br-TADAP complex was determined. The λ max of the complex is 590 nm and the ε 590 is 8.24 × 10 4 L · mol -1 cm -1. Once formed, the Co (II) -5-Br-TADAP complex can no longer be decomposed by the addition of EDTA, but can decompose many complexes of other metal ions with the reagent. Beer’s law is obeyed in the range of 0-20 micrograms of cobalt in a volume of 25 milliliters. The method is simple, rapid, accurate and reliable, and is applied to the determination of small and trace cobalt in low alloy steel. The results are satisfactory.