METHOD FOR PREPARING SODIUM FLUORIDES Russian patent published in 2003 - IPC

FIELD: inorganic chemistry, chemical technology, chemical industry. SUBSTANCE: gaseous hydrogen fluoride is added to 10-20% sodium hydroxide solution. Self-heating temperature of solution is 60-90C. In attainment the stoichiometric ratio of reagents feeding hydrogen fluoride is ceased. In preparing sodium fluoride the stoichiometric ratio of reagents are determined by the first change of electrode potential from 600-700 mV to 540-615 mV and in preparing sodium hydrodifluoride by the second value from 600-700 mV to 160-185 mV. Tungsten electrode in pair with chloride-silver electrode through salt key of potassium chloride is used. Prepared precipitate is separated from mother liquor and dried on filter under vacuum. Invention provides reducing energy consumptions due to self-heating solution, to diminish losses of end product due to improvement of its filtration capacity, to enhance the yield of NaF up to 99-99.97 wt.-% and that of NaHF₂ - up to 96.3-98.55 wt.-%. Invention can be used in preparing sorbents for extraction of volatile fluorides from gaseous flows. EFFECT: improved preparing method. 5 cl, 2 tbl, 1 ex