Calcium fluoride

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Calcium fluoride
Calcium fluoride.jpg Fluorite-unit-cell-3D-ionic.png
Fluorid vápenatý.PNG
Identifiers
CAS number 7789-75-5 YesY
PubChem 24617
ChemSpider 23019 YesY
UNII O3B55K4YKI YesY
EC number 232-188-7
ChEBI CHEBI:35437 YesY
RTECS number EW1760000
Jmol-3D images Image 1
Properties
Molecular formula CaF2
Molar mass 78.07 g mol−1
Appearance White crystalline solid (single crystals are transparent)
Density 3.18 g/cm3
Melting point 1,418 °C (2,584 °F; 1,691 K)
Boiling point 2,533 °C (4,591 °F; 2,806 K)
Solubility in water 0.0015 g/100 mL (18 °C)
0.0016 g/100 mL (20 °C)
Solubility product, Ksp 3.9 × 10−11 [1]
Solubility insoluble in acetone
slightly soluble in acid
Refractive index (nD) 1.4338
Structure
Crystal structure cubic crystal system, cF12[2]
Space group Fm3m, #225
Coordination
geometry
Ca, 8, cubic
F, 4, tetrahedral
Hazards
EU Index Not listed
R-phrases R20, R22, R36, R37, R38
S-phrases S26, S36
Main hazards Reacts with conc. sulfuric acid to produce hydrofluoric acid
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g., sodium chloride Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
LD50 4250 mg/kg (oral, rat)
Related compounds
Other anions Calcium chloride
Calcium bromide
Calcium iodide
Other cations Beryllium fluoride
Magnesium fluoride
Strontium fluoride
Barium fluoride
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Calcium fluoride is the inorganic compound with the formula CaF2. It is a colourless insoluble solid. It occurs as the mineral fluorite (also called fluorspar), which is often deeply coloured owing to impurities.

Chemical structure[edit]

The compound crystallizes in a cubic motif. Ca2+ centres are eight-coordinate, being centered in a "box" for eight F centres. Each F centre is coordinated to four Ca2+ centre.[3] Although perfectly packed crystalline samples are colorless, the mineral is often deeply colored due to the presence of F-centers.

The unit cell of CaF2.

Preparation[edit]

The mineral fluorspar is abundant, widespread, and mainly of interest as a precursor to HF. Thus, little motivation exists for the industrial production of CaF2. High purity CaF2 is produced by treating calcium carbonate with hydrofluoric acid:[4]

CaCO3 + 2 HF → CaF2 + CO2 + H2O

Applications[edit]

Main article: fluorite

Naturally occurring CaF2 is the principal source of hydrogen fluoride, a commodity chemical used to produce a wide range of materials. Calcium fluoride in the fluorite state is of significant commercial importance as a fluoride source.[5] Hydrogen fluoride is liberated from the mineral by the action of concentrated sulfuric acid:[6]

CaF2 + H2SO4CaSO4(solid) + 2 HF

Safety[edit]

CaF2 is classified "not dangerous." With regards to inhalation, the NIOSH-recommended concentration of fluorine-containing dusts is 2.5 mg/m3 in air.[4]

References[edit]

  1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0-07-049439-8
  2. ^ X-ray Diffraction Investigations of CaF2 at High Pressure, L. Gerward, J. S. Olsen, S. Steenstrup, M. Malinowski, S. Åsbrink and A. Waskowska, Journal of Applied Crystallography (1992), 25, 578-581 doi:10.1107/S0021889892004096
  3. ^ G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
  4. ^ a b Aigueperse, Jean; Paul Mollard, Didier Devilliers, Marius Chemla, Robert Faron, Renée Romano, Jean Pierre Cuer (2005), "Fluorine Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a11_307 
  5. ^ Aigueperse, Jean; Mollard, Paul; Devilliers, Didier; Chemla, Marius; Faron, Robert; Romano, Renée; Cuer, Jean Pierre (2005), "Fluorine Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, p. 307, doi:10.1002/14356007.a11_307.
  6. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.

See also[edit]

Related materials[edit]

External links[edit]