本文研究了铁(Ⅲ)与5-Cl-PADAP的显色反应。研究表明,在pH3—6的乙酸-乙酸钠缓冲介质中显色,络合物的最大吸收波长位于605 m处,摩尔吸光系数为8.82×10~4。络合物的组成比及稳定常数分别是Fe:5-Cl-PADAP=1:2和K_稳=3. 86×10~(11)。铁量在0—20μg/25mL范围内符合比尔定律。方法已用于金属铝、镁及其合金和无机化工原料中痕量铁的测定,操作简便、快速、方法灵敏、准确。 In this paper, the color reaction of iron (Ⅲ) with 5-Cl-PADAP was studied. The results showed that the maximum absorption wavelength of complex was at 605 m at pH3-6 in acetic acid-sodium acetate buffer medium, and the molar absorptivity was 8.82 × 10 ~ 4. The composition ratio and the stability constants of the complexes are Fe: 5-Cl-PADAP = 1: 2 and K-steady = 3.86 × 10-11. Beer’s law is obeyed in the iron range of 0-20 μg / 25 mL. The method has been applied to the determination of trace iron in metallic aluminum, magnesium and their alloys and inorganic chemical raw materials. The method is simple, rapid, sensitive and accurate.