Hydrogen Fluoride
Structural Formula Vector Image
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.

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