Calcium fluoride, decomposition

Dissolution occurring to belong to protonation involves the processes highlighted out in Table 5.2. The dissolution of calcium carbonate in acids, the decomposition of calcium fluoride by concentrated sulfuric acid, the dissolution of ferrous sulfide in hydrochloric acid are some of the examples that can be pointed out as protonation-based dissolution. 

Silicon tetrafluoride has been prepared by the reaction1 of concentrated sulfuric acid with a mixture of sand and calcium fluoride, at room temperature or upon mild heating. However, the product is contaminated by hydrofluoric and fluorosilicic acids. J The thermal decomposition of barium hexafluorosilicate2 is a convenient method, requiring simple apparatus and capable of producing silicon tetrafluoride of high purity. 

A rapid procedure has been described10 based on sodium peroxide bomb fusion, for the determination of silicon and halogen in fluorine-containing organosilicon compounds and resins. The silicon is separated from the decomposition product as zinc silicate and estimated gravimetrically as silica. The filtrate is concentrated, acidified and, when necessary, reduced with sulphur dioxide. Chloride, bromide or iodide is then determined by the usual methods. Fluoride can be determined in neutral solution either gravimetrically as calcium fluoride, or volumetrically with zirconium tetrachloride or thorium nitrate, or directly in the decomposition solution by titration with zirconium tetrachloride. 

Precipitated tertiary calcium phosphate, under the same conditions, reacts after a few minutes due to production of acid-insoluble zirconium phosphate. The decomposition of the zirconium-alizarin lake is not instantaneous as in the case of calcium fluoride probably because the color lake is adsorbed by zirconium phosphate, which is the initial product. This supposition is supported by the finding that zirconium phosphate is reddened immediately by contact with an acid zirconium-alizarin solution. 

There is also the possibility of a double decomposition reaction leading to the precipitation of insoluble calcium fluoride ... 

Phosphoms oxyfluoride is a colorless gas which is susceptible to hydrolysis. It can be formed by the reaction of PF with water, and it can undergo further hydrolysis to form a mixture of fluorophosphoric acids. It reacts with HF to form PF. It can be prepared by fluorination of phosphoms oxytrichloride using HF, AsF, or SbF. It can also be prepared by the reaction of calcium phosphate and ammonium fluoride (40), by the oxidization of PF with NO2CI (41) and NOCl (42) in the presence of ozone (43) by the thermal decomposition of strontium fluorophosphate hydrate (44) by thermal decomposition of CaPO F 2H20 (45) and reaction of SiF and P2O5 (46). 

Fluorhydroxyapatite can be synthesised by the traditional double-decomposition method generally used for apatite precipitation. An ammonium phosphate and fluoride solution (solution B) is added, dropwise, into a hot (generally at boiling temperature) calcium solution (solution A) at a basic pH level as previously published [122,123]. Fluorapatites close to stoichiometry are obtained (a = 2, see the following reaction equation) however, a very small residual amount of OH always seems to be present. Filtration and several washing operations are necessary to remove the counter-ions. The reaction is almost total due to the very low solubility of fluorhydroxyapatites. 

SAFETY PROFILE Moderately toxic by intraperitoneal route. Mildly toxic by ingestion. An experimental teratogen. Other experimental reproductive effects. Mutation data reported. See also FLUORIDES and CALCIUM COMPOUNDS. When heated to decomposition it emits toxic fumes of F . 

Na NaOH H2SO4 vinyl acetate HgO sodium tetrafluoro silicate n-phenyl azo piperidine. Incandescent reaction of liquid HF with oxides (e.g., arsenic trioxide, calcium oxide). Dangerous storage hazard with nitric acid + lactic acid nitric acid + propylene glycol (mixtures evolve gas which may burst a sealed container). Reacts with water or steam to produce toxic and corrosive fumes. When heated to decomposition it emits highly corrosive fumes of F . See also FLUORIDES. 

Derivation (1) Reduction of thorium dioxide with calcium (2) fused salt electrolysis of the double fluoride ThF4 KF. The product of both processes is thorium powder, fabricated into the metal by powder metallurgy techniques. Hot surface decomposition of the iodide produces crystal bar thorium. 

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