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二苯胺磺酸钠是测定铁和铬等常用的氧化还原指示剂,由于二苯胺磺酸钠不可逆地氧化为二苯联苯胺磺酸,然后被氧化成二苯联苯胺磺酸紫,因此指示剂校正值比较大。为了减少指示剂校正值对测定准确度的影响,文献提出用二苯胺磺酸钠氧化型的悬浮体作指示剂,但制备方法繁琐,易出沉淀,而且在硫酸亚铁滴定铬酸根和钒酸根时,校正值仍然偏大。本文推荐用二苯联苯胺磺酸紫作指示剂。指示剂配制:称取0.2克二苯胺磺酸钠,0.075克重铭酸钾,加80毫升水溶解,加磷酸(10%)20毫升,摇匀即可使用。
Sodium diphenylamine sulfonate is a commonly used redox indicator for the determination of iron and chromium. Since sodium diphenylamine sulfonate is irreversibly oxidized to dibenzidine sulfonic acid and then oxidized to dibenzidine sulfonic acid, the indicator Correction value is relatively large. In order to reduce the influence of the correction value of the indicator on the determination accuracy, the literature proposes to use sodium diphenylamine sulfonate as the indicator, but the preparation method is cumbersome and easy to precipitate. In addition, titration of ferrous sulfate with vanadate When the correction is still too large. This article recommends using diphenylbenzidine sulfonic acid as indicator. Indicator formulation: Weigh 0.2 grams of sodium diphenylamine sulfonate, 0.075 grams of potassium base Ming, dissolved in 80 ml of water, add phosphoric acid (10%) 20 ml, shake can be used.