：采用二次回归正交设计法系统地研究了 Ｃｒ （ Ⅲ） —５ － Ｂｒ － Ｐ Ａ Ｄ Ａ Ｐ— Ｄ Ｅ Ａ 三元配合物显色反应的最佳条件，建立了测定 Ｃｒ （ Ⅲ） 的新方法，ε５９５ｍａｘ ＝ ５ ．７ ×１０４ Ｌ·ｍｏｌ－ １·ｃｍ － １ 。将该方法用于合成水样和４０ 号铬钒钢中铬含量的测定，结果令人满意。并通过紫外—可见及红外光谱对该配合物的分子结构进行了研究，推断出该三元配合物的配位情况 The optimum conditions for the chromogenic reaction of Cr (Ⅲ) -5 - Br - P A D A P - D E A ternary complex were systematically investigated by the quadratic regression orthogonal design method. The new method, ε595max = 5. 7 × 104 L · mol-1 · cm-1. The method was applied to the determination of chromium in synthetic water samples and chrome vanadium steel No. 40 with satisfactory results. The molecular structure of the complex was studied by ultraviolet-visible and infrared spectroscopy, and the coordination of the ternary complex was deduced