Calcium fluorinated compounds

Production Technology. Processes for extraction of P2O3 from phosphate rock by sulfuric acid vary widely, but all produce a phosphoric acid—calcium sulfate slurry that requires soHds-Hquid separation (usually by filtration (qv)), countercurrent washing of the soHds to improve P2O3 recovery, and concentration of the acid. Volatilized fluorine compounds are scmbbed and calcium sulfate is disposed of in a variety of ways. 

Although stable at ambieat temperature, calcium fluoride is slowly hydrolyzed by moist air at about 1200°C, presumably to CaO and HF. Calcium fluoride is not attacked by alkahes or by reactive fluorine compounds, but is decomposed by hot, high boiling acids, as ia the reactioa with coaceatrated sulfuric acid which is the process used to produce hydrogea fluoride. Calcium fluoride is slightly soluble ia cold dilute acids, and somewhat more soluble ia solutioas of alumiaum hahdes. 

Most of the acid-grade spar used for HF production ia the United States is imported. More than two-thkds of the fluorspar consumed ia the United States goes iato production of HF nearly 30% is consumed as a flux ia steelmaking and the remainder is consumed ia glass manufacture, enamels, welding rod coatings, and other end uses or products (see Fluorine compounds, inorganic-calcium). 

Calcium fluoride calcined with potassium fluoride affords benzyl fluoride (4) in 81% yield from benzyl bromide (3) on refluxing in acetonitrile.2,3 This reagent has been sucessfully used in the preparation of various other organo-fluorine compounds. 

Enamel -fluorspar in prdn of [FLUORINE COMPOUNDS, INORGANIC - CALCIUM] (Volll) -in food packaging [FOOD PACKAGING] (Vol 11) -NDE of [NONDESTRUCTIVE EVALUATION] (Vol 17)... 

Lenses - [ALLYL MONOMERS AND POLYMERS] (Vol 2) -ofcalcium fluorite [FLUORINE COMPOUNDS, INORGANIC - CALCIUM] (Vol 11) -fromCR-39 [ALLYL MONOMERS AND POLYMERS] (Vol 2) -glasses for [CERAMICS - GLASS STRUCTURE AND PROPERTIES] (Vol 5) -refractory coatings for [REFRACTORYCOATINGS] (Vol21) -selenium m infrared [SELENIUM AND SELENIUM COMPOUNDS] (Vol 21) -ofvitreous silica [SILICA - VITREOUS SILICA] (Vol21)... 

The residue from the treatment with acetic arid is again incinerated together with the filter, the ash being mixed with precipitated silica or calcium silicate or even finely powdered sand and introduced into a platinum crucible the mass is then moistened with a little concentrated sulphuric arid and the crucible immediately covered with a glass plate having a drop of water on its lower side. In case the ash contained fluorine compounds, there will appear, after a few moments and without heating, a deposit of silica on the edges of the water-drop. 

The fluorine in fluoride toothpaste is in the form of a fluorine compound. One such compound is sodium monofluoride phosphate. The fluorine in the sodium monofluoride phosphate bonds with calcium in tooth enamel and forms a calcium fluoride layer that acts as a bacterial barrier. 

The world s major source of phosphorus is apatite, a class of phosphate minerals. Commercially, the most important is fluoroapatite, a calcium phosphate that contains fluorine. This fluorine must be removed for the manufacture of phosphoric acid, but it also can be used to produce hydrofluoric acid and fluorinated compounds. 

The F content in recent bone or dentine apatite is normally less than 0.1 wt.%. For ancient specimen, F is known to diffuse during burial into bone material. Its enrichment is generally a part of many complex diagenetic changes of bone and tooth, which remains after their deposit. Fluorine can react with the bone and dentine mineral phase to form calcium fluoride compounds. It usually substitutes for hydroxyl ions in hydroxyapatite, leading to the less soluble fluorapatite compound (Ca10(PO4)6(F)2, FAP). 

Like many lanthanoids, pure thulium is made by treating its fluorine compound with calcium ... 

Ruorine comes from the Latin wordfluere, which means to flow. The mineral fluorite, which contains fluorine and calcium, is used to lower the melting points of other minerals to make it easier to separate them from their ores. Fluorine compounds are added to toothpaste and drinking water to protect tooth enamel from decay. A compound of fluorine and carbon provides a non-stick coating for the cookware shown in Figure 7-20a. When fluorine reacts with isotopes of uranium, the gases that form are separated by differences in mass. This process is called uranium enrichment it provides the uranium-235 fuel for nuclear reactors. 

Fluorine compounds added to toothpaste and public drinking-water supplies have greatly reduced the incidence of cavities. Fluoride protects teeth in two ways. As teeth form, fluoride from food and drink is incorporated into the enamel layer. The fluoride makes the enamel stronger and more resistant to decay. Once teeth are present in the mouth, fluoride in saliva bonds to teeth and strengthens the surface enamel. This surface fluoride attracts calcium, which helps to fill in areas where decay has begun. 

Phosphate rock preparation—Domestic phosphate rocks are essentially fluorapatite admixed with various proportions of other compounds of calcium, fluorine, iron, aluminum, and silicon. Phosphate rock preparation involves beneficiation to remove impurities, drying to remove moisture, and grinding to improve reactivity. Phosphate rock, when very finely pulverized, has limited direct use as a fertilizer. However, it is mainly used as a raw material for the manufacture of phosphate acid, superphosphate, phosphorus, and phosphorus compounds. 

Additives used in final products Fillers antimony trioxide, aramid, barium sulfate, boron nitride, calcinated kaolin, carbon black, carbon fiber, glass fiber, glass spheres, mica, montmorillonite, talc, titanium dioxide, zinc borate Antistatics antimony-doped tin oxide, carbon nanotubes, polyaniline, polyisonaphthalene Antiblocking calcium carbonate, diatomaceous earth, silicone fluid, spherical silicone resin, synthetic silica Release calcium stearate, fluorine compounds, glycerol bistearate, pentaerythritol ester, silane modified silica, zinc stearate Slip spherical silica, silicone oil ... 

Antiblocking calcium carbonate, diatomaceous earth, silicone fluid, spherical silicone resin, synthetic silica Release calcium stearate, fluorine compounds, glycerol bistearate, pentaerythritol ester, silane modified silica, zinc stearate Slip spherical silica, silicone oil... 

Phosphoric Acid 40 158 70 G G (29% P Os). sulfuric acid 2-3%, slurry contains 2-3% calcium sulfate dihydrate (gypsum), 0.5% fluorine compounds as hydrofluosilicic acid, metallic compounds... 

Phosphoric Acid 55 221-261 105-127 U u (40% PjO ), sulfuric acid 3.0% (2.5% SO3). calcium sulfate (hemihydrate) slurry fluorine compounds. Liquid phase, gases containing HjO and Si i are evolved Foam distribution process... 

---