依据在酸性条件下,铈Ce(IV)的强氧化性使丽春红S褪色的原理,建立了一种褪色光度法测定微量铈的新方法。实验结果表明:丽春红S溶液的最大吸收波长为510 nm,铈量在0～5.0 mg/L范围内遵循比尔定律,线性回归方程为:y=0.0048x-0.0068,相关系数为r=0.9993,表观摩尔吸光系数为ε510=2.18×104L.mol-1.cm-1。新方法用于稀土氧化物中微量铈的测定,样品分析结果的相对标准偏差为0.99%(n=5),加标回收率为96.9%～99.0%。 Based on the principle of cerium (IV) strong oxidizing property that discolor Ponceau S under acidic conditions, a new method for the determination of trace cerium by fading spectrophotometry was established. The experimental results show that the maximum absorption wavelength of Li Chunhong S solution is 510 nm, Beer’s law is obeyed in the range of 0-5.0 mg / L, the linear regression equation is y = 0.0048x-0.0068, the correlation coefficient is r = 0.9993 , The apparent molar absorptivity ε510 = 2.18 × 104L.mol-1.cm-1. The new method was applied to the determination of trace cerium in rare earth oxides. The relative standard deviation of sample analysis was 0.99% (n = 5), and the recoveries were 96.9% ~ 99.0%.