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在Ｐｈ ２．７—３．４的乙酸－乙酸钠缓冲溶液中，在沸水浴中加热２０ｍｉｎ，铬（Ⅲ）与２－（２－噻吩偶氮）－５－二乙氨基酚（ＴＡＤＡＰ）生成稳定的１：２ 螯合物，最大吸收波长λｍａｘ＝５６５ｎｍ，摩尔吸光系数。ε＝６．２４ｘ１０~４，铬（Ⅲ）浓度在０～１２μｇ／２５ｍＬ范围内遵守比尔定律，铬（Ⅲ）螯合物吸光度值至少可稳定４８ｈ．研究了干扰离子的影响及消除方法．本法具有较高的灵敏度和较好的选择性．用于电镀废水中铬的测定，获得了满意的结果．
Chromium (Ⅲ) and 2- (2-thiophene azo) -5-diethylaminophenol (TADAP) were generated by heating in a boiling water bath in acetic acid-sodium acetate buffer solution of Ph 2.7-3.4 Stable 1: 2 chelate, maximum absorption wavelength λmax = 565nm, molar extinction coefficient. ε = 6.24 × 10 ~ 4, Beer’s law was obeyed in the range of 0 ~ 12μg / 25mL for chromium (Ⅲ). The absorbance of chromium (Ⅲ) chelates was stable for at least 48h. The influence of interference ions and the elimination method are studied. This law has higher sensitivity and better selectivity. For electroplating wastewater determination of chromium, obtained satisfactory results.