Abstract：Lime is favored by the iron and steel metallurgy industry for its superior slagging performance. The main components of lime are calcium oxide and magnesium oxide. It is very important to efficiently and accurately determine the contents of calcium oxide and magnesium oxide in lime. During the determination of calcium oxide and magnesium oxide in lime by complexometric titration method in national standard GB/T 3286.1-2012, the process is cumbersome and time-consuming. Moreover, the judgement of titration endpoint by eyes could easily cause visual error. Therefore, the method cannot meet the production requirements of dynamic process control in the smelting process. The sample was dissolved with hydrochloric acid. Triethanolamine was added into sample solution to mask the interference of Fe3+ and Al3+. Dextrin was added to inhibit the adsorption of calcium by a large amount of magnesium hydroxide precipitates in the sample solution. The contents of calcium oxide and magnesium oxide were determined by potentiometric titration using ethylenediaminetetraacetic acid (EDTA) standard solution in strong alkaline medium. Two treatment methods, i.e., recovering and not recovering the insoluble matter in the sample solution after dissolution with hydrochloric acid, were investigated, respectively. The t-test of determination results of calcium oxide and magnesium oxide was conducted, and it was found that there was no significant difference. The contents of calcium oxide and magnesium oxide in three lime samples were determined according to the experimental method. The relative standard deviations (RSD, n=11) of the results were all less than 0.5%. A batch of lime samples were selected for the determination of calcium oxide and magnesium oxide according to the method and GB/T 3286.1-2012, respectively. The differences of two methods were less than ±0.20% and ±0.10% for calcium and magnesium, respectively. The titration endpoint was judged by the potential jump, which could reduce the visual error of the personnel in judging the titration endpoint. The proposed method could meet the determination requirements of the dynamic control in smelting process.
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