重铬酸钾容量法测定铁矿石中亚铁含量方法的改进

建立了以邻菲罗啉(Phen)、氢氟酸(HF)和硫酸(H2 SO4)为溶剂溶解试样,用重铬酸钾滴定法测定铁矿中亚铁含量的新方法.在强酸(H2 SO4)介质中,Fe2与邻菲罗啉和氟离子形成稳定的络合物,有效地防止了亚铁离子的氧化.在硼酸、硫磷混酸溶液中,以重铬酸钾溶液滴定,并对溶样过程以及滴定过程中的一些条件进行了优化.方法用于铁矿中氧化亚铁的测定,经过国家标准样品以及单位管理样品分析数据对比,方法的重现性较好,相对标准偏差(RSD)＜1％,方法无需在铂金坩埚进行熔样,具有准确度高、重现性好、简单、快速、经济等优点,在实际应用中得到满意的结果.

Method Improvement for Determination of Ferrous Iron in Iron Ore by Potassium Dichromate Volumetry

In this study, a fast and simple approach to directly determineferrous iron in iron ore samples by potassium dichromate volumetry was developed using 1,10-phenanthroline monohydrate (Phen), hydrofluoric acid (HF) and sulfuric acid (H2SO4) for sample dissolution. In sulfuric acid(H2SO4) medium, Fe2+ reacted with Phen and fluorine ion to form a stable complex compound, which might effectively prevent the oxidation of ferrous ion. The ferrous iron was directly titrated with potassium dichromate standard solution in a mixed acid H3BO3-H2SO4-H3PO4 using sodium diphenylamine sulfonate as the indicator. Experimental parameters were optimizedand analytical figures of merit were evaluated.The proposed method has been successfullyapplied to the determination offerrous oxide in iron ore.Comparing the analytical results of the certified reference materialswith those of realiron ore samples, it was found that the proposed method had a good reproducibility with the standard deviation of less than 1%. The method did not needa platinum crucible to melt samples, and had some advantages of high accuracy, good reproducibility, simple operation, fast analytical speed and low cost.