Catalytic Spectrophotometry Determination of Trace Rhodium(Ⅲ) with Rhodamine S-KIO₄ System

Based on the catalytic effects of rhodium(Ⅲ) on the colour fading reactions of Rhodamine S by oxidizing with KIO₄,a new catalytic spectrophotometric method for the determination of rhodium(Ⅲ) has been developed.The optimum condition and kinetic parameters of this reaction was studied in detail.The results show that in sulphuric acid medium and at 90±0.5℃,the method has higher sensitivity,the linear range of the determination was 10~140 μg/L,the detection limit was 5.0×10^-9 g/mL,and the apparent activation energy of catalytic reaction was 64.86 kJ/mol.The method has been applied to the determination of Rhodium in its composite samples with satisfactory results.