The color reaction between Co(Ⅲ) and 2-(5-Bromo-2-thiazolylazo) -5-dimethylaminobenzoic acid(5-Br-TAMB) has been studied. The experimental results show that in the presence of ethanol at pH 3.7~5.4
Co (Ⅲ)reacts with 5-Br-TAMB to form a stable blue 1:2 complex with apparent molar absorptivity of 1.09×105L·mol cm at 684 nm. Beer's law is obeyed in the range of 0~15μg/25ml for CO(Ⅲ). The method has