恒电流库仑分析法测定铬矿中三氧化二铬

在0.1mol/LH2SO4-H3PO4介质中电解0.02mol/LFe2(SO4)3溶液,使Pt阴极上产生Fe2+;采用H2SO4-H3PO4-(NH4)2S2O8分解铬矿,用KMnO4将其中Cr3+氧化为Cr2O27-;以Fe2+对Cr2O27-进行库仑滴定,采用永停终点法确定库仑滴定终点,根据电解定律计算三氧化二铬含量。用本法和硫酸亚铁铵滴定法分别测定铬矿标样中三氧化二铬,本法相对误差为0.22%,RSD(n=11)为0.034%,测定结果的准确度和精密度明显高于硫酸亚铁铵滴定法。

Determination of Cr2O3 content in chromium mineral by the constant current coulometric analysis

The solution of 0.02 mol/L Fe_2(SO_4)_3 is electrolyzed in the medium of 0.1 mol/L H_2SO_4-H_3PO_4 to produce Fe~ 2 in the platinum cathode. The chromium mineral is dissolved in a mixture of H_2SO_4, H_3PO_4 and (NH_4)_2S_2O_8 and Cr~ 3 in the solution is oxidized to Cr_2O~ 2- _7 by KMnO_4,which is titrated by the Fe~ 2 .The reactions are quantitative proceeding.The end point of the titration is confirmed by the forever stop end point method. The content of Cr_2O_3 in chromium mineral is calculated based on the electrolyse law. The proposed method and the titration with ferrous ammonium sulfate are served to the determination of Cr_2O_3 in a standard sample of chromium mineral, respectively. The relative deviation and relative standard deviation of proposed method are 0.22% and 0.034%(n=11). The accuracy and precision of the method are higher than those of the titration with ferrous ammonium sulfate.