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用(NH_4)_2S_2O_8氧化显色光度法同时测定钢铁中铬和锰,在国内外的分析化学教课书中已列为学生实验。但按文献操作将出现两个“异常”现象: 1.试样经1:1硫—磷混酸溶解后,在AgNO_3存在下用(NH_4)_2S_2O_8氧化时,Mn~(2+)和cr~(3+)始终不显色。 2.在制备工作曲线时,将一定体积的KMnO_4和K_1Cr_2O_7标准溶液按给定条件处理试样,则颜色褪去而出现低价锰和三价铬
Simultaneous determination of chromium and manganese in steel with (NH_4) _2S_2O_8 oxidation chromogenic spectrophotometry has been listed as a student experiment in analytical chemistry teaching books at home and abroad. However, there are two “abnormal” phenomena according to the literature: 1. After the sample is dissolved with 1: 1 Sulfur-Phosphoric acid and oxidized with (NH 4) 2 S 2 O 8 in the presence of AgNO 3, 3+) No color development at all. 2. In the preparation of the working curve, a certain volume of KMnO_4 and K_1Cr_2O_7 standard solution treated according to the given conditions of the sample, the color fade and appear cheap manganese and trivalent chromium