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研究了对碘偶氮氯膦（ＣＰＡ－ｐＩ）与Ｂｉ（Ⅲ）的显色反应，并用以测定合金中的微量铋。试验表明：在０．１０ｍｏｌ／ＬＨＣｌＯ４介质中，Ｂｉ（Ⅲ）与ＣＰＡ－ｐＩ形成１：３的蓝绿色络合物。显色剂的吸收峰位于５５０ｎｍ，络合物的吸收峰在６８０ｎｍ处，其表观摩尔吸光系数ε６８０＝６．４８×１０４Ｌ·ｍｏｌ－１·ｃｍ－１。Ｂｉ（Ⅲ）浓度在０～９５７×１０－６ｍｏｌ／Ｌ（即０～２．０μｇ／ｍｌ）范围符合比尔定律。测定了近３０种共存离子的影响，大多数常见离子对测定干扰较少。方法用于测定铸造铝合金与焊锡中的微量铋，结果满意。
The color reaction of iodine chlorophosphonazo (CPA-pI) with Bi (Ⅲ) was studied and the trace amounts of bismuth in the alloy were determined. Experiments show that: in 0.10mol / LHClO4 medium, Bi (Ⅲ) and CPA-pI form a 1: 3 cyan complex. The absorption peak of the color reagent is at 550 nm, and the absorption peak of the complex is at 680 nm. The apparent molar absorptivity ε680 = 6.48 × 104 L · mol-1 · cm-1. Beer’s law is obeyed for the concentration of Bi (Ⅲ) in the range of 0-957 × 10-6mol / L (ie, 0-2.0μg / ml). The influence of nearly 30 kinds of coexisting ions was measured, and most common ions did not interfere with the measurement. The method was applied to the determination of trace bismuth in the cast aluminum alloy and solder, and the results were satisfactory.