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pH4．5时，Mo（Ⅵ）与显色剂4-（2-苯并噻唑偶氮）邻苯二酚反应形成带负电荷的稳定紫红色1∶2二元络合物。40％丙酮水溶液中λmax为560nm，表现ε560为6.33X104L·mol-1·cm-1。它可与二苯胍进一步反应形成电中性的稳定紫红色1∶2∶1三元离子缔合络合物。其氯仿萃取液的λmax为546nm，表现ε5460为7．56X104L·mol-1·cm-1。Mo（Ⅵ）含量在0．02～0．72mg／L范围内均遵从比耳定律。建议了两种络合物的结构。三元体系具有更好的选择性。将拟定的分析方法用于合金钢试样中小量或痕量钼的测定，取得了满意的结果。
At pH 4.5, Mo (VI) reacts with the color reagent 4- (2-benzothiazolylazo) catechol to form a negatively charged, stable purplish red 1: 2 binary complex. Λmax in 40% acetone aqueous solution was 560 nm, which showed that ε560 was 6.33 × 104 L · mol-1 · cm-1. It can react further with diphenylguanidine to form an electrically neutral, stable fuchsine 1: 2: 1 ternary ion-association complex. The λmax of its chloroform extract was 546 nm, indicating that ε5460 was 7.56 × 10 4 L · mol -1 · cm -1. Beer’s law is obeyed for the content of Mo (Ⅵ) in the range of 0.02 ~ 0.72mg / L. The structure of two complexes is suggested. Ternary system has a better selectivity. The proposed analytical method is applied to the determination of small or trace amounts of molybdenum in the alloy steel samples, and satisfactory results have been obtained.