Calcium fluoride
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Identifiers | |||
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3D model (
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ChEBI | |||
ChemSpider | |||
ECHA InfoCard
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100.029.262 | ||
EC Number |
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RTECS number
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CompTox Dashboard (EPA)
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Properties | |||
CaF2 | |||
Molar mass | 78.075 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) | ||
0.015 g/L (18 °C) 0.016 g/L (20 °C) | |||
Solubility product (Ksp)
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3.9 × 10−11 [1] | ||
Solubility | insoluble in acetone slightly soluble in acid | ||
-28.0·10−6 cm3/mol | |||
Refractive index (nD)
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1.4338 | ||
Structure | |||
cubic crystal system, cF12[2] | |||
Fm3m, #225 | |||
a = 5.451 Å, b = 5.451 Å, c = 5.451 Å α = 90°, β = 90°, γ = 90°
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Ca, 8, cubic F, 4, tetrahedral | |||
Hazards | |||
Occupational safety and health (OHS/OSH): | |||
Main hazards
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Reacts with concentrated sulfuric acid to produce hydrofluoric acid | ||
NFPA 704 (fire diamond) | |||
Flash point | Non-flammable | ||
Lethal dose or concentration (LD, LC): | |||
LDLo (lowest published)
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>5000 mg/kg (oral, guinea pig) 4250 mg/kg (oral, rat)[3] | ||
Safety data sheet (SDS) | ICSC 1323 | ||
Related compounds | |||
Other anions
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Calcium chloride Calcium bromide Calcium iodide | ||
Other cations
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Beryllium fluoride Magnesium fluoride Strontium fluoride Barium fluoride | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Calcium fluoride is the inorganic compound of the elements calcium and fluorine with the formula CaF2. It is a white solid that is practically insoluble in water. It occurs as the mineral fluorite (also called fluorspar), which is often deeply coloured owing to impurities.
Chemical structure
The compound crystallizes in a cubic motif called the fluorite structure.
Ca2+ centres are eight-coordinate, being centered in a cube of eight F− centres. Each F− centre is coordinated to four Ca2+ centres in the shape of a tetrahedron.[5] Although perfectly packed crystalline samples are colorless, the mineral is often deeply colored due to the presence of F-centers. The same crystal structure is found in numerous ionic compounds with formula AB2, such as
Gas phase
The gas phase is noteworthy for failing the predictions of
Preparation
The mineral fluorite 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:[10]
- CaCO3 + 2 HF → CaF2 + CO2 + H2O
Applications
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.[11] Hydrogen fluoride is liberated from the mineral by the action of concentrated sulfuric acid:[12]
- CaF2 + H2SO4 → CaSO4(solid) + 2 HF
Others
Calcium fluoride is used to manufacture optical components such as windows and lenses, used in thermal imaging systems, spectroscopy,
Doped calcium fluoride, like natural fluorite, exhibits thermoluminescence and is used in thermoluminescent dosimeters. It forms when fluorine combines with calcium.[citation needed]
Safety
CaF2 is classified as "not dangerous", although reacting it with sulfuric acid produces hydrofluoric acid, which is highly corrosive and toxic. With regards to inhalation, the NIOSH-recommended concentration of fluorine-containing dusts is 2.5 mg/m3 in air.[10]
See also
References
- ISBN 0-07-049439-8
- ^ "Fluorides (as F)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
- S2CID 119056949.
- ISBN 0-13-035471-6.
- ISBN 978-0-08-037941-8.
- PMID 15852152.
- .
- hdl:10486/7315.
- ^ ISBN 978-3527306732.
- ^ 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.
- ISBN 0-12-352651-5.
External links
- NIST webbook thermochemistry data
- Charles Townes on the history of lasers
- National Pollutant Inventory - Fluoride and compounds fact sheet
- Crystran Material Data Archived 2012-11-10 at the Wayback Machine
- MSDS Archived 2011-11-21 at the Wayback Machine (University of Oxford)