研究了 2 (4 氯 2 膦酸基苯偶氮 ) 7 (4 氟苯偶氮 ) 1,8 二羟基 3 ,6 萘二磺酸 (对氟偶氮氯膦 )与铋的显色反应。在0 2 6mol/L硝酸介质中 ,铋与对氟偶氮氯膦形成 1∶2的深蓝色络合物 ,最大吸收波长 664nm ,摩尔吸光系数为 1 2 0× 10 5,Bi 含量在 0～ 2 0 μg/ 2 5mL范围内符合比尔定律 ,方法操作简便 ,灵敏度高 ,选择性好 ,用于可锻铸铁中微量铋的测定 ,结果满意 The color reaction of 2 (4-chloro-2-phosphonophenylazo) 7 (4-fluorophenylazo) 1,8 dihydroxy 3,6 naphthalenedisulfonic acid (p-fluoro-chlorophosphonazo) with bismuth was studied. In 0 2 6mol / L nitric acid medium, bismuth forms a 1: 2 dark blue complex with fluoro-chlorophosphonazo, the maximum absorption wavelength is 664nm, the molar absorptivity is 120 × 10 5, and the Bi content is 0 ~ Beer’s law was obeyed in the range of 20 μg / mL and 5 mL. The method was simple, sensitive and selective. The method was applied to the determination of trace bismuth in malleable cast iron with satisfactory results