Hydrogen Fluoride

Title: Hydrogen Fluoride
CAS Registry Number: 7664-39-3
CAS Name: Hydrofluoric acid gas
Additional Names: fluohydric acid gas; anhydr hydrofluoric acid
Molecular Formula: FH
Molecular Weight: 20.01
Percent Composition: F 94.94%, H 5.04%
Line Formula: HF
Literature References: Obtained by the action of sulfuric acid on fluorspar (calcium fluoride): Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 462-467; prepn of pure HF: Simons, Inorg. Synth. 1, 134 (1939); Shamir, Netzer, J. Sci. Instrum. (Ser. 2) 1, 770 (1968). Exists as hydrogen-bonded polymers: Simons, Hildebrand, J. Am. Chem. Soc. 46, 2183 (1924); Jarry, Davis, J. Phys. Chem. 57, 600 (1953); Atoji, Lipscomb, Acta Crystallogr. 7, 173 (1954). pKa determn: N. E. Vanderborgh, Talanta 15, 1009 (1968). Cryoscopic determn: R. J. Gillespie, D. A. Humphreys, J. Chem. Soc. A 1970, 2311. Toxicity study: M. J. Rosenholtz et al., Am. Ind. Hyg. Assoc. J. 24, 253 (1963). Review of prepn, properties and chemistry: Simons in Fluorine Chemistry vol. 1, J. H. Simons, Ed. (Academic Press, New York, 1950); Hyman, Katz, "Liquid Hydrogen Fluoride" in Non-aqueous Solvent Systems, T. C. Waddington, Ed. (Academic Press, New York, 1965) pp 47-81; O'Donnell in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1038-1054; J. F. Gall in Kirk-Othmer Encyclopedia of Chemical Technology vol. 10 (Wiley-Interscience, New York, 3rd ed., 1980) pp 733-753; of toxicology and human exposure: Toxicological Profile for Fluorides, Hydrogen Fluoride, and Fluorine (PB2004-100002, 2003) 404 pp.
Properties: Colorless gas. Fumes in air. Highly irritating, corrosive and poisonous! d34 1.27 (air = 1); d04 1.002. mp -83.57°. bp 19.51°; bp400 2.5°; bp200 -13.2°; bp100 -28.2°; bp40 -45.0°; bp20 -56.0°; bp5 -74.7°. Very sol in water and alcohol. Slightly sol in ether. Sol in many organic solvents; soly (wt % at 5°): benzene 2.54; toluene 1.80; m-xylene 1.28; tetralin 0.27. Many compds are sol in HF. Anhydr HF is one of the most acidic substances known; Hammett acidity function (H0) -10.98. Weak acid in aqueous soln. pKa 3.189. Forms a constant boiling mixture with water, see hydrofluoric acid. Dissolves silica, silicic acid, glass. Store in steel cylinders. LC50 (15 min.) in rats, guinea pigs: 2689, 4327 ppm (Rosenholtz).
Melting point: mp -83.57°
Boiling point: bp 19.51°; bp400 2.5°; bp200 -13.2°; bp100 -28.2°; bp40 -45.0°; bp20 -56.0°; bp5 -74.7°
pKa: pKa 3.189
Density: d34 1.27 (air = 1); d04 1.002
Toxicity data: LC50 (15 min.) in rats, guinea pigs: 2689, 4327 ppm (Rosenholtz)
CAUTION: Potential symptoms of overexposure are irritation of eyes, skin, nose and throat; pulmonary edema; skin and eye burns; rhinitis; bronchitis; bone changes. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 168. See also Patty's Industrial Hygiene and Toxicology vol. 2B, G. D. Clayton, F. E. Clayton, Eds. (Wiley-Interscience, New York, 3rd ed., 1981) pp 2945-2948.
Use: Catalyst, especially in the petroleum industry (paraffin alkylation); in fluorination processes, especially in the aluminum industry; in the manuf of fluorides; for separating uranium isotopes; in making fluorine contg plastics; in dye chemistry.
Hydrogen Iodide Hydrogen Selenide Hydrogen Sulfide Hydrogen Telluride Hydrogen Tetracarbonylferrate(II)

Hydrogen fluoride
Hydrogen-fluoride-2D-dimensions.png Hydrogen-fluoride-3D-vdW.png
Identifiers
CAS number 7664-39-3 YesY
PubChem 16211014
ChemSpider 14214 YesY
UNII RGL5YE86CZ YesY
KEGG C16487 YesY
ChEBI CHEBI:29228 YesY
RTECS number MW7875000
Jmol-3D images Image 1
Properties
Molecular formula HF
Molar mass 20.01 g mol−1
Appearance colorless gas
Density 1.15 g/L, gas (25 °C)
0.99 g/mL, liquid (19.5 °C)
Melting point −83.6 °C; −118.5 °F; 189.6 K
Boiling point 19.5 °C; 67.1 °F; 292.6 K
Solubility in water miscible
Acidity (pKa) 3.17[1][2]
Refractive index (nD) 1.00001
Structure
Molecular shape Linear
Dipole moment 1.86 D
Thermochemistry
Std molar
entropy So298
8.687 J/g K (gas)
Std enthalpy of
formation ΔfHo298
−13.66 kJ/g (gas)
−14.99 kJ/g (liquid)
Hazards
NFPA 704
NFPA 704.svg
0
4
1
Related compounds
Other anions Hydrogen chloride
Hydrogen bromide
Hydrogen iodide
Other cations Sodium fluoride
Related compounds Hydrofluoric acid
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers (e.g. Teflon). HF is widely used in the petrochemical industry and is a component of many superacids. Hydrogen fluoride boils just below room temperature whereas the other hydrogen halides condense at much lower temperatures. Unlike the other hydrogen halides, HF is lighter than air and diffuses relatively quickly through porous substances.

Hydrogen fluoride is a highly dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with tissue. The gas can also cause blindness by rapid destruction of the corneas.

French chemist Edmond Frémy (1814–1894) is credited with discovering anhydrous hydrogen fluoride while trying to isolate fluorine, although Carl Wilhelm Scheele prepared hydrofluoric acid in large quantities in 1771, and this acid was known about in the glass industry before then.