Spectrophotometric determination of palladium in ore with 4-(5-chloro-2-pyridine)-azo-1,3-diaminobenzene
4（5氯2吡啶）偶氮1，3二氨基苯光度法测定矿石中钯

In 1.80 mol/L sulfuric acid medium,the chromogenic reagent 4-(5-chloro-2-pyridine)-azo-1,3-diaminobenzene(5-Cl-PADAB) could react with palladium to form a colored complex.At the maximum absorption wavelength of this complex(570 nm),Beer’s law was obeyed between absorbance and palladium concentration.The determination method of palladium was established on the basis of this.The coloring conditions of palladium were tested.The coloring medium,coloring time and dosage of 5-Cl-PADAB were obtained.The interference of more than 30 ions was investigated.The result indicated that only Pb2+,Ag+ and Cr had serious interference in the determination of palladium.However,the interference of Pb2+,Ag+ and Cr  could be eliminated by the following method: Pb2+ and Ag+ were precipitated in sulfuric acid and hydrochloric acid,respectively;anhydrous ethyl alcohol was added into acid solution,and then Cr  was reduced to Cr by heating.Thus,the determination of palladium was realized.Beer’s law was obeyed for palladium in the concentration range of 0-1.2 mg/L.The apparent molar absorptivity was 6.38×104 L·mol-1·cm-1.The proposed method was successfully applied to the determination of palladium(above 0.05 g/t) in common ore sample.