Abstract：In (CH2)6N4-HCl buffer solution and in the presence of OP emulsifier trace Ni(Ⅱ) catalyzes strongly the decolorization reaction of Rhodamine B (RhB) by oxidizing with H2O2，and its catalytic extent is linear with the contents of Ni(Ⅱ) in a certain range. Based on this study，a novel spectrophotometric method for determining Ni(Ⅱ) was developed. The results show that the maximum absorption of the complex is at 550 nm，the detection limit of the method is 0.4 μ g·L-1for Ni(Ⅱ)，and Beer’s law is obeyed for Ni(Ⅱ) in the range of 0-0.3 mg·L-1. The method has been applied to the determination of Ni in FeNiCr alloys with satisfactory results.
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