Chemistry of inorganic compounds – Silicon or compound thereof – Oxygen containing
Patent
1987-07-27
1991-10-08
Doll, John
Chemistry of inorganic compounds
Silicon or compound thereof
Oxygen containing
423178, 423341, C01B 3324, C01B 3308, C01F 100, C01F 506
Patent
active
050552813
ABSTRACT:
Process for the production of anhydrous calcium fluosilicate from anhydrous calcium chloride and impure fluosilicic acid solution, a by-product of the acid treatment of phosphorus ores containing fluorine, characterized in that a calcium fluosilicate dihydrate is precipitated at low temperature and quantitatively by suitable adjustment of the fluosilicic acid concentration and the molar ratio CaCl.sub.2 /H.sub.2 SiF.sub.6 and that after filtration, washing and drying of the precipitate, an anhydrous calcium fluosilicate which can be easily decomposed by heat treatment is obtained to restore calcium fluoride and silicon tetrafluoride suitable for the manufacture of pure hydrofluoric acid and fluosilicic acid.
For gravimetric concentrations of H.sub.2 SiF.sub.6 >25% and molar concentration ratios CaCl.sub.2 /H.sub.2 SiF.sub.6 between 2 and 5, the yields of the anhydrous calcium fluosilicate obtained are greater than 94%.
REFERENCES:
patent: 2780523 (1957-02-01), Glass
patent: 4765772 (1988-08-01), Benedetti et al.
Inorganic and Theoretical Chemistry, vol. VI, Mellor, 1947, pp. 951-952.
Ryss, The Chemistry of Flourine and its Inorganic Compounds-Part I, p. 416.
Aluminum Pechiney
Doll John
Freeman Lori S.
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