Nomenclature
CAS number: 7664-39-3
Hydrofluoric acid gas; fluohydric acid gas; anhydr hydrofluoric acid.
FH; mol wt 20.01.
F 94.94%, H 5.04%.
HF.
Description and 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.
Corrosive, poisonous. d
34 1.27 (air = 1); d
04 1.002. mp 83.57°. bp 19.51°; bp
400 2.5°; bp
200 13.2°; bp
100 28.2°; bp
40 45.0°; bp
20 56.0°; bp
5 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 (H
0) 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. LC
50 (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.