Fluoride minerals

FLUORITE. Fluorite is a calcium fluoride mineral CaFi crystallizing in the isometric system, often in superb cubic crystals. Twinned crystals are common, usually as cubic penetration twins. It is found in many diverse... 

E, Sorensen, Ox (he Adsorption or Some Anionic Collectors on Fluoride Minerals, J. Colloid... 

The adsorption maximum at pH 9-10 has been seen by others [26] as reflecting the first of silicic acid (pA l = 9.45 at 25°C), although it has been argued by different workers that this maximum in turn was an indication that SiO(OH)J adsorbed alone [29] or that Si(OH)4 and SiO(OH)J adsorbed concurrently [26]. Early modeling studies [26,28] related silica adsorption to exchange with substrate surface hydroxyl groups, although clearly this situation would not be the case for adsorption on fluoride minerals. Davis and Leckie... 

Remineralization can occur at the tooth surface by the diffusion of calcium and phosphate ions from the saliva into the tooth surface, followed by precipitation. This precipitation occurs at nucleation sites on the surfaces of the remaining crystals within the tooth and occurs because the saliva is saturated with respect to calcium and phosphate ions [12], Remineralization is enhanced by the presence of fluoride and results in a new mineral phase, which contains a small amount of fluoride ion. The resulting lightly fluoridated mineral phase is more resistant to add attack than the native carbonated hydroxyapatite [12]. 

Klemm, W. A., Jawed, L, and Holub, K.J. (1979) Effect of calcium fluoride mineralization on silicate and melt formation in Portland cement clinker. Cement and Concrete Research 9,489-496. 

The two largest sources of cerium and other rare earth elements are the minerals hastnasite and monazite. Bastnasite, which belongs to carbonate-fluoride minerals, exists as several types bastnasite-(Ce) (Ce, La)C03p bastnasite-(La) (La, Ce)C03F and bastnasite-(Y) (Y, Ce)C03F. The most frequently occurring of these is bastnasite-(Ce), and cerium is by far the most common of the rare earths in this class of minerals. 

Fluorine is a highly reactive element, so it is not found in nature in its elemental form. Pure fluorine must be recovered Ifom a variety of fluoride minerals, including fluorite (CaF2) and cryoHte (Na3AIF6). Many chemists have been injured by explosive... 

A few fluoride minerals of rare earths are known, but none for chlorides, bromides and iodides. Simple oxides of the rare earths are very rare in nature and no rare earth sulfide mineral is known. 

T.T. Tran, Fluoride mineralization of Portland cement, applicatiotis of doubleresonance NMR spectroscopy in structural investigations of guest ions in cement phases, PhD thesis, in 2011. 

However, in 1886, American engineer Charles Martin Hall and French engineer Paul Heroult simultaneously but independently announced that they had discovered how to electrowin aluminum metal from alumina. Because aluminum oxide melts at such a high temperature (i.e., 2030 C) and is a nonionic (i.e., nonconductive) Hquid, electrolysis of the molten oxide is not feasible. What both Hall and Heroult discovered was that a natural fluoride mineral called cryolite (i.e., Na AlF, monoclinic), which occurs naturally in Greenland and melts at only 1009 C, would act as fluxing agent and easily dissolve purified aluminum oxide. This molten salt mixture could then be electrolyzed using carbon electrodes. 

Most substances that contain F are soluble. A common fluoride mineral is fluorite, CaF, which occurs in a variety of colors including purple, green, and yellow. Likewise, in rule 4, most substances that contain SO 4 are soluble, mostly with the exception of some of the alkaline earths and the lead ion. 

Only one calcium halide is known to have been used as a pigment, die calcium fluoride mineral fluorite q.v.). However, it has been suggested that bone (widely known as a pigment and used eidier as a white calcination product or a black coke) is to be considered a fluorinated calcium phosphate, fluorapatite (qq.v.). 

R. B. Ferguson, Observations on some aluminium fluoride minerals. Am. Mineral, 34, 383-397 (1949). 

The main source of fluoride in ground water is fluoride-bearing rocks such as fluorospar, fluorite, eiyolite, fluorapatite and hydroxylapatite [12]. The flouride content in ground water is a function of several faetors including hydrogeological environment, solubility of fluoride minerals in water, velocity of flowing water, pH, temperature as well as coneentrations of other species such as calcium and bicarbonate ions in water [13,14]. 

E. J. Sorensen. On the adsorption of some anionic collectors on fluoride minerals. J. Colloids Interface Sci. 45, 1973, 601. 

Cyclic formats of 1,3-glycols are prepared by patented proces.ses involA -ing the reactions of olefins A i,th formaidehyde in the presence of acidic catalA-sts,. such as boron fluoride, mineral acids, zinc chloride,... 

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