METHOD OF CALCIUM FLUORIDE PRODUCING Russian patent published in 1997 - IPC

FIELD: chemical technology, inorganic chemistry. SUBSTANCE: method involves precipitation of sodium silicofluoride from fluoride-containing solution with sodium salt, hydrolysis of sodium silicofluoride with ammonia in an aqueous medium, preparing ammonium fluoride, chalk addition and producing the end product. About 15-70% of total ammonium fluoride solution amount is treated with sodium chloride and sodium fluoride deposit formed is separated from mother liquor and used for sodium silicofluoride precipitation. The parent chalk is treated with mother liquor and the obtained solid product containing unreacted chalk is separated from liquid and used for ammonium fluoride conversion. Method ensures to replace soda with more available sodium chloride. EFFECT: decreased reagent consumption and cost. 2 cl, 1 tbl