Fluorine fluorite

Fluorine fluorite fluor-apatite cryolite hydrogen fluoride hydrofluoric acid silicon tetrafluoride sodium fluoride oxygen fluoride. 

Fluorine occurs widely in nature as insoluble fluorides. Calcium fluoride occurs as jluospar or fluorite, for example in Derbyshire where it is coloured blue and called bluejohn . Other important minerals are cryolite NajAlFg (p. 141) and Jluorapatite CaFjSCaj (P04)2. Bones and teeth contain fluorides and some natural water contains traces. 

Analytical Methods. Fluorite is readily identified by its crystal shape, usually simple cubes or interpenetrating twins, by its prominent octahedral cleavage, its relative softness, and the production of hydrogen fluoride when treated with sulfuric acid, evidenced by etching of glass. The presence of fluorite in ore specimens, or when associated with other fluorine-containing minerals, may be deterrnined by x-ray diffraction. 

Eluorspar assay may be completed by fluoride determination alone, because the mineralogical grouping rarely iacludes fluorine minerals other than fluorite. Calcium can be determined as oxalate or by ion-selective electrodes (67). SiUca can be determined ia the residue from solution ia perchloric acid—boric acid mixture by measuriag the loss ia weight on Aiming off with hydrofluoric acid. Another method for determining siUca ia fluorspar is the ASTM Standard Test Method E463-72. 

The structure can be instructively compared with that of fluorite, CaF2. In fluorite the calcium ions are arranged at face-centered lattice points, and each is surrounded by eight fluorine ions at cube corners. 

No compound containing a halogen other than chlorine appears among the top 50 industrial chemicals, but fluorine nevertheless has considerable commercial value. Fluorine occurs as the mineral fluorite (CaF2) and is prevalent in phosphate-bearing rock. As already mentioned, HF produced from sulfiaric acid treatment of fluorite supplies some 70% of industrial HF the remainder comes as a by-product of phosphoric acid production. 

There are numerous minerals that contain halogens. Minerals that contain fluorine include fluorite, CaF2, cryolite, Na3AlFs, and fluoroapatite, Ca5(P04)3F. As was discussed in Chapter 14, fluoroapatite is found with calcium phosphate, which is very important in the production of fertilizers. Fluorite is found in Southeastern Illinois and Northwestern Kentucky, and cryolite is found in Greenland, although it is also produced synthetically because of its use in the electrochemical production of aluminum. 

As a final example, we consider a fluid of known fluoride concentration whose calcium content is set by equilibrium with fluorite (CaF2). The speciation of fluorine provides for two solutions to this problem. In dilute solutions, in which the free ion I dominates, the reaction,... 

To use react to discover the root at low Ca++ concentration, we swap fluorite for Ca++ and arbitrarily set a 1 molal NaCl solution of pH 5 that contains slightly less than 1 mmolal fluorine. We set temperature to 200 °C... 

By this reaction, we can expect the modeled fluid to be rather acidic, since it is rich in potassium. We could have chosen to fix pH by equilibrium with the siderite, which also occurs in the veins. It is not clear, however, that the siderite was deposited during the same paragenetic stages as the fluorite. It is difficult on chemical grounds, furthermore, to reconcile coexistence of the calcium-rich ore fluid and siderite with the absence of calcite (CaCOs ) in the district. In any event, assuming equilibrium with kaolinite leads to a fluid rich in fluorine and, hence, to an attractive mechanism for forming fluorite ore. 

Figure 22.1 shows the mineralogic results of tracing the reaction path. As the fluid cools by 50 °C, it produces about 1.8 cm3 of fluorite and 0.02 cm3 of quartz. No other minerals form. From a plot of the concentration of fluorine-bearing species (Fig. 22.2), it is clear that the fluorite forms in response to progressive break-... 

Interstitial positions, positions in a crystal not normally occupied by an atom, are denoted by the subscript i. For example, F would represent an interstitial fluorine atom in, say, a crystal of fluorite, CaF2. 

The most abundant fluorine mineral is fluorite—calcium fluoride (CaF )— which is often found with other minerals, such as quartz, barite, calcite, sphalerite, and galena. It is mined in... 

Calcium fluoride occurs in nature as the mineral fluorspar or fluorite. It is used as a flux in ferrous metallurgy to enhance the fluidity of the slag. An important application of this compound is in the manufacture of fluorine and hydrofluoric acid, starting materials for producing many fluoroorganics. It also is used in glass and ceramics. Pure crystals are used in lasers, optics, and electronics. Other applications are in high temperature, dry-film lubricants ... 

One may conclude that the above-mentioned anhydrous [ F]fluorine compounds, except perhaps H[ F]F, have been abandoned, partly because of their limited potential and difficulty of preparation and also because of the success of the main three agents of today, [ F]fluoride (see Section 4), p F]fluorine gas (see Section 3.1.1) and acetyl [ F]hypofluorite (see Section 3.1.3). The advent of the first one, ([ F]fluoride), made less urgent the need for high-specific-activity electrophilic fluorine and the latter two, ([ F]fluorine gas and acetyl p F]hypo-fluorite), are able to perform practically all low-specific-activity electrophilic syntheses (see Section 3), putting a brake on the development of alternatives. 

Fluorite is calcium fluoride, Cap2, with a cubic face-centered lattice, while each fluorine ion is at the center of one of the smaller cubes obtained by dividing the unit cube into eight parts. Each Ca is coordinated by eight F ions and each F is surrounded by four Ca ions arranged at the corners of a regular tetrahedron. 

Fluorine for industrial use is almost exclusively obtained from fluorite. There are many possible fluorite-ore types. It occurs as fissure-fill and manto-replaced types, and in pegmatites, residual/eluvial deposits, carbonates and phosphate deposits. It is a gangue mineral in many base metal deposits, but due to stringent trace metal requirements often can t be economically beneficiated to a saleable product. Most fluorite ores are selectively mined, and ore from some minor vein deposits is then upgraded to a saleable product by sorting. 

CaFa, mw 78.08, wh pdr, sp gr 3.18 at 20°, mp 1330° nearly in sol in w si sol in ale reacts with hot coned sulfuric acid to liberate HF. Can be prepd by, powdering pure fluorite or by the interaction of soluble Ca salt and NaF. Used in manuf of HF, ceramics, smelting, cements, etching of glass, etc. Clear cryst is used in optical equipment. Was used by E. Turpin in expls named Fluorine , described in Vol 6, under "Explosifs de Turpin Refs 1) Gmelin-Kraut Syst Number 28(1956),... 

Fluorine compounds from fluorite (fluorspar, CaF2) are used in water treatment (to suppress dental caries) and to make fluoropolymers (such as Teflon), lubricants, and refrigerants. Molten cryolite (Na3AlF6) is essential as a solvent for Al203 in the electrolytic production of aluminum metal, while the isotopic enrichment of uranium for nuclear power reactors is usually achieved by diffusion or gas centrifugation of volatile UF6. 

The major ones are fluorapatite (general formula Ca5 [ F/OH/CI j (P04)3 - also called phosphate rock) and fluorspar (CaF2 - sometimes called fluorite) see Finger, G.C. Adr. Fluorine Chem. 1961, 2, 35... 

Naming structure 9 pcrfluorobutanal nicely illustrates the important rule (quoted earlier) that hydrogen atoms forming part of a functional group remain unsubstituted by fluorine (structure 10 is, of course, an acyl fluoride) likewise perfluoropropanoic acid is 5 not 11 (an acyl hypo-fluorite), while perfluoropiperidine is 12 not 13 (perfluoro-l-fluoropiperidine). 

Low-temperature fluorination of sodium acetate in suspension gives a mixture of acetyl hypo-fluorite (AcOF, 1, R = Me) and alkyl hypofluorite the crude mixture can be used, in some cases, directly for the introduction of fluorine into organic molecules. The course of the reaction strongly depends on the reaction conditions and, when the fluoride anion is quenched with hydrogen fluoride or water, trifluoroacetyl hypofluorite (1, R = CF3), 3 acetyl hypofluorite (1, R = Me) and long-chain acid fluorites are obtained.4-6 On the other hand, an excess of fluorine can lead to the formation of alkyl fluoroxy compounds 2 or geminal bis(fluoroxy) products 3. 

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