This part specifies the method for the determination of fluorine content in continuous casting protective slag using fluorine Ion selective electrode method. It is suitable for the determination range of fluorine content in continuous casting protective slag from 0.50% to 15.00%. The relevant safety precautions should be carefully read and understood before use. If necessary, the user should have practical experience in laboratory work. The test material is melted with sodiumhydrate and sodium peroxide. After being leached with water, the total ion strength adjustment buffer solution is added. Then the fluorine content is directly determined by fluorine Ion selective electrode method. During the analysis, only approved analytical pure reagents and distillation water or water of equivalent purity that meets the regulations should be used.