Abstract：A method was introduced for the determination of calcium oxide and calcium fluoride in KR molten iron desulphurizer. By taking advantage of alkaline characteristics of activated calcium oxide in KR molten iron desulphurizer, the sample was dissolved by excess hydrochloric acid, and the excessive hydrochloric acid was back-titrated by sodium hydroxide standard solution with phenolphthalein as indicator. Thus the content of calcium oxide could be calculated by deducting the consumption of hydrochloric acid by magnesium oxide. Simultaneously, in consideration of the acid-soluble characteristics of calcium oxide and calcium fluoride in KR molten iron desulphurizer, the samples were dissolved by hydrochloric acid. After iron and aluminum was separated by precipitation with hexamethylenetetramine, their interference was further masked by triethanolamine solution in acidic solution. Being adjusted to pH 12 with potassium hydroxide solution, the content of total calcium was determined by EDTA complexometry (national method) with calcein as indicator. Being adjusted to pH 8-9 with ammonia buffer solution, the total content of calcium and magnesium was determined by EDTA complexometry with acid chrome blue K-naphthol B green as indicator. Thereby the content of magnesium was obtained by subtraction. In KR molten iron desulphurizer, the content of calcium fluoride was determined indirectly by deduction of the content of active calcium oxide from the content of total calcium and the formula calculation. A number of parallel determinations of KR molten iron desulphurizer synthetic samples were carried out with this method. The results were consistent with the reference values, and the relative standard deviations (RSDs, n=6)) were less than 1%. Recovery test was conducted by adding calcium fluoride and calcium oxide certified reference materials, and the recoveries were between 97% and 102%.
