Fluorite solubility

Nordstrom, D. K. Jenne, E. A. 1977. Fluorite solubility equilibria in selected geothermal waters. Geochimica et Cosmochimica Acta, 41, 175-188. 

The control of fluoride concentration by fluorite (CaF2) saturation is likely in some waters. Fluorite solubility has been shown to be a complex function of temperature, salinity, and major ion chemistry (Holland and Malinin, 1979 Richardson and Holland, 1979). Hitchon (1995) found that lower salinity waters of the Alberta Basin are generally undersaturated with respect to fluorite, and that there is a gradual increase in fluoride to CaF2 saturation as temperature and salinity increase. 

The data presented in Figure 1 and Tkble III illustrate that upon recarbonation and exposure to the sandstone, the activity of Ca + in the leachate most closely approaches equilibrium with calcite. Both before and after reaction with the sandstone, Ca activity is undersaturated with respect to gypsum and fluorite and oversaturated with respect to dolomite. The gypsum and fluorite solubility lines in Figure 1 were developed using 804 and F activities calculated in the raw leachate. 

Fig. 12.3. Solubility diagram for fluorite as a function of calcium ion activity at 200 °C (solid) and 300 °C (dashed lines). Fluorite is soluble at a specific activity (horizontal line) either as F at small Ca++ activity (point A) or as CaF+ at high Ca++ activity (point B).

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),... 

Deep groundwaters from igneous rocks are usually saturated with respect to CaC03, which limits the maximum Ca2 -concentration and thereby also indirectly determines the F"- and H2P04"-concen-trations due to the limited solubility of CaF2 and Ca-phosphates. Both F" and H2PO4" are usually found in the groundwater due to the presence of accessory minerals like fluorite and apatite in the rock. 

Calcium Fluoride. [CAS 7789-75-51. CaF.-. white precipitate, formed by reaction of soluble calcium salt solution and sodium fluoride solution. pK = 10.40. See also Fluorite. 

The structure of platinum dioxide and its reactions with some di, tri, and tetravalent metal oxides have been investigated. Ternary platinum oxides were synthesized at high pressure (40 kUobars) and temperature (to 1600°C). Properties of the systems were studied by x-ray, thermal analysis, and infrared methods. Complete miscibility is observed in most PtO2-rutile-type oxide systems, but no miscibility or compound formation is found with fluorite dioxides. Lead dioxide reacts with Pt02 to form cubic Pb2Pt207. Several corundum-type sesquioxides exhibit measurable solubility in PtOz. Two series of compounds are formed with metal monoxides M2PtOh (where M is Mg, Zn, Cd) and MPt306 (where M is Mg, Co, Ni, Cu, Zn, Cd, and Hg). 

In soils, F can be found in four major fractions (1) dissolved in soil solution (2) sorbed to Al, Fe, and Mn oxides and hydroxides and carbonates (3) solid phases, such as fluorite and fluorophlogopite and (4) associated with organic compounds. The solubility of F in soil solution is variable and is affected by pH, speciation, adsorption and desorption reactions, and dissolution and precipitation reactions (Luther et al., 1996). Acidic conditions and low calcium carbonate content are favorable to F solubility and can therefore enhance both root uptake (Weinstein and Alscher-Herman, 1982) and migration to surface and ground water (Smith, 1983). These conditions can lead to human, plant, and animal health issues. Soils that do contain appreciable amounts of calcium carbonate and are neutral to slightly alkaline conditions can fix F as insoluble calcium fluoride (CaF2), and reduce its bioavailability and mobility (Kubota et al., 1982 Tracy et al., 1984 Reddy et al., 1993 Poulsen and Dudas, 1998). 

Th02 White, crystalline fluorite structure 3220 Stable, refractory, soluble in HF + HN03... 

Fluorite. The solubility and related thermodynamic properties of fluorite have had large uncertainties, i.e. 2 to 3 orders of magnitude. Nordstrom and Jenne (50) utilized simul-... 

The conductivities of some ceria-containing compounds obtained from the literature have been compiled and shown as solid lines in Fig. 2.12. The main dopants for ceria belong to the alkaline earth or rare-earth metal series and the majority of doped samples exhibit conductivity values which fall into a rather limited band (gray band in Fig. 2.12), which points to a similar behaviour for all doped ceria samples. Exceptions are pure ceria and ceria doped with redox elements like Pr and Tb which give rise to electronic contribution to conductivity. An important requirement is that a homogeneous solid solution forms between the two oxides, which maintains the fluorite structure since the presence of a second phase or phase inhomogeneity due to insufficient solubility can affect ionic conductivity. The very low values of conductivity found for BaO and MgO-doped ceria were in fact attributed to the low solubility of these oxides into the lattice of When the... 

Most parts of the oceans are nearly saturated with CaF2. The mineral fluorite, CaF2, may precipitate when ocean water evaporates. A saturated solution of CaF2 at 25°C has a solubility of 3.4 x 10 " M. Calculate the solubility product constant for CaF2. 

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