【摘要】 本文研究了新显色剂-2-〔2- （3,5-二溴吡啶）偶氮〕-5-二乙氨基苯甲酸（3, 5-diBr-PAEB）与钴的显色反应。在pH2.1—5.4的Triton X-l00介质中,钴可与3,5-diBr-PAEB形成稳定的绿色配合物。其最大吸收峰位于673nm,摩尔吸光率5₆₇₃=1.52×10⁵L.mol^-1·m^-1。反应具有较好的选择性,共存元素中,仅铜、镍、铁、锰、钒等有一定干扰,其它金属离子在一定限量内对钴的显色反应没有干扰。而上述干扰离子也可采用适当的掩蔽剂消除影响。因此,反应可直接用于各种钢铁试样中微量钴的分光光度法测定。结果堪称满意。更多还原

【Abstract】 A new chromogenic reagent 2 -[2-（3, 5-dibromopyridyl）azo]-5 -diethylaminobenzoic acid（3, 5-diBr-PAEB）has been synthesized and its colour reaction with Co ions was studied spectrophotometrically. Both in the absence and in the presence of nonionic surfactant Triton X-100 the acid dissociation constants of 3, 5-diBr-PAEB were determined. In the acid medium with pH range of 2. 1—5. 4, 3, 5-diBr-PAEB reacts with Co ions to form a stable complex exhibiting a maximum absorbance at 673 nm. Its apparent molar absorptivity is found to be 1. 52×10⁵ L. mol^-1. cm^-1. The molar ratio of Co: 3, 5-diBr-PAEB in the complex was estimated as 1: 3 by different methods. Common metal ions did not interfere with the determination of Co. Interferences from Cu, Ni, Fe and Cr ions can be eliminated by masking with fluoride and sodium citrate. The proposed method has been used for the trace Co in low-alloy steels and pig irons with satisfactory results.更多还原