Study on the Color Reaction of Palladium with Chlorophosphonazo Ⅲ and Its Application

The color reaction between palladium and chlorophosphonazo Ⅲ has been studied. It was found that palladium reacts with chlorophosphonazo Ⅲ to form a 1:1 blue complex in H₂SO₄ medium. The complex exhibits a maximum absorption at 644 nm with an apparent molar absorptivity of 2.4×10⁴ L/(mol·cm). Beer's law is obeyed in the range of 0.1～1.5 mg/L Pd(Ⅱ). The method proposed was applied to the determination of palladium in refined ore and anode mud samples with satisfactory results.