A characteristic that Mn(Ⅲ)has a strong absorption near 485 nm,but Mn(Ⅱ)does not have.Based on this characteristic,a simple and accurate method through the spectrophotometry to determinate the concentration of the oxalic acid oxidized rapidly by Mn(Ⅲ)was established.The effects of sulfuric acid concentrations and reaction time on the decomposition rate of the oxalic acid were revealed.The results indicate that optimum conditions for a H2SO4concentration used in preserving Mn(Ⅲ)and determining H2C2O4concentrations that is 2.625 M,a detecting...