EDTA络合滴定法测定钢渣面脱氧剂中氧化钙和氟化钙

建立了EDAT络合滴定法测定钢渣面脱氧剂中氧化钙和氟化钙含量的分析方法。试样用碳酸钠-硼酸混合熔剂熔融, 稀盐酸浸取, 六次甲基四胺分离铝离子和铁离子后, 以三乙醇胺掩蔽剩余干扰离子, 在强碱介质中, 以钙黄绿素作指示剂, 用EDTA标准滴定溶液滴定了试样中总氧化钙的含量。采用稀乙酸浸取分离试样中碳酸钙、氧化钙, 过滤分离氟化钙, 用锆-二甲酚橙褪色光度法测定了浸取液中的氟, 换算为氟化钙的量;同时用混合酸分解沉淀, 采用EDTA络合滴定法测定了沉淀中氟化钙的量;将二者相加后除以试样总量得到试样中氟化钙的含量。用总氧化钙的含量减去由氟化钙换算成的氧化钙含量, 即为试样中氧化钙的含量。采用方法对钢渣面脱氧剂试样进行6次平行测定, 相对标准偏差(RSD)小于1.5 %。选取高纯铝粉、基准三氧化二铝和基准氧化钙以及萤石标准物质合成钢渣面脱氧剂试样A1、A2、A3, 同时在精炼渣标准物质中加入基准氧化钙和萤石标准物质合成试样A4, 按照方法进行氧化钙和氟化钙的测定, 结果与理论值一致。在钢渣面脱氧剂试样中加入基准氧化钙和萤石标准物质进行加标回收试验, 回收率在94%～102%之间。

Determination of calcium oxide and calcium fluoride in steel slag powder deoxidizer by EDTA complexometric titration

A method was introduced for the determination of calcium oxide and calcium fluoride in steel slag powder deoxidizer by EDTA complexometric titration. After the sample was melted by mixed flux of sodium carbonate and boric acid and leached by diluted hydrochloric acid, hexamethylenetetramine was used to separate the ions of iron and aluminum, and triethanolamine was used to mask the remaining interference ions. In strong alkali medium, the content of total calcium oxide in samples was titrated by EDTA standard titration solution with calcein as indicator. By leaching separation method with acetic acid, calcium carbonate and calcium oxide were leached, and calcium fluoride was filtered and separated. Fluoride in leaching solution was determined by fading spectrophotometry with zirconium-xylenol orange, which was changed into the amount of calcium fluoride. Simultaneously, calcium fluoride in the precipitation was determined by EDTA complexometric titration after decomposed with mixed acid. Then, the content of calcium fluoride in the sample was the sum of them divided by the sample mass.Subsequently, the content of total calcium oxide minus the content of calcium oxide, converted from the content of calcium oxide, to obtain the content of calcium oxide in the sample.This method was used for six parallel determinations of steel slag powder deoxidizer samples. The relative standard deviations (RSD) were less than 1.5%. The samples A1, A2, A3 of steel slag powder deoxidizer were synthesized by high purity aluminum powder, aluminium oxide and calcium fluoride of primary reagent, and fluorite certified reference materials, and the samples A4 of steel slag powder deoxidizer was synthesized by adding calcium oxide of primary reagent and fluorite certified reference material into refining slag certified reference material. This method was applied to determination of these samples, and the results were in accordance with the theoretical value. The recovery test was conducted by adding calcium oxide of primary reagent and fluorite certified reference materials into the steel slag powder deoxidizer samples with recoveries of 94%-102%.