Nomenclature
CAS number: 10035-10-6
Anhydrous hydrobromic acid.
BrH; mol wt 80.91.
Br 98.76%, H 1.25%.
HBr.
Description and references
Prepd commercially by direct combination of
the elements at 375° preferably over a catalyst such as platinized
silica gel or platinized asbestos: Richards, Hnigschmid, J. Am. Chem. Soc. 32, 1581 (1910);
Smyth, Hitchcock, ibid. 55, 1830 (1933); Schneider, Johnson, Inorg.
Synth. 1, 152 (1939). Lab procedure from tetrahydronaphthalene
and bromine: Müller, Monatsh. Chem. 49, 29 (1928); Duncan, Inorg.
Synth. 1, 151 (1939); Schmeisser in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd
ed., 1963) pp 282-286. Detailed description of laboratory methods
of prepn: Houben-Weyl, Methoden der organischen
Chemie vol 5/4 (Thieme, Stuttgart, 4th ed.,
1960) p 16-20. Review of prepn and properties of HBr and other hydrogen
halides: Woolf in Mellor's vol. II, Suppl I (originally published as Suppl II, part 1)
724-741 (1956); John in Bromine and its Compounds, Z. E. Jolles, Ed. (Ernest Benn, London, 1966) pp 81-105; Downs,
Adams in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon
Press, Oxford, 1973) pp 1280-1329.
Properties
Colorless, nonflammable gas. Acrid odor. Fumes
in moist air forming clouds which have a sour taste. d 2.71 (air = 1.00). mp 86.9°. bp
760 66.8°; bp
11.0 atm 4.8°; bp
17.1 atm 12°; bp
30.0 atm 36°; bp
59.2 atm 70°. Crit temp 89.8°; crit press. 84.5 atm. Sp heat
(cal/g/°C): solid (91°) 0.152; liquid 0.176; gas (27°) 0.085. Heat
of fusion at mp: 7.44 cal/g. Heat of vaporization at bp: 51.3 cal/g.
Poisonous, corrosive. Freely
sol in water: One vol H
2O dissolves 600 vols HBr gas at
0°. Also sol in alc. Soly in organic solvents: Fernandes,
J. Chem. Eng. Data 17, 377 (1972);
Gerrard,
Chem. Ind. (London) 1969, 295; Ahmed
et al., J. Appl. Chem. 20, 109 (1970). Aq solns are
strongly acid. The satd aq soln contains 68.85% HBr at 0° and 66%
at 25°. The boiling point of a constant-boiling mixture is 122.5°
at 740 mm and 126° at 760 mm. The composition of the constant-boiling
mixture is 47.38% HBr at 752 mm. For complete tables
see Bonner
et al., J. Am. Chem. Soc. 55, 1406 (1943).
See also Hydrobromic Acid. Anhydr HBr is marketed in steel cylinders
in the form of a gas over liquid. LC
50 in mice, rats: 814, 2858 ppm by inhalation, K. C. Back
et al., Reclassification
of Materials Listed as Transportation Health Hazards (TSA-20-72-3,
PB 214-270, 1972).
Caution
Potential symptoms of overexposure
are irritation of eyes, skin, nose and throat; direct contact with
solutions may cause skin and eye burns; direct contact with liquid
may cause frostbite. See NIOSH
Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997)
p 166.Use
Mfg organic and inorganic bromides, hydrobromic
acid, as reducing agent and as catalyst in controlled oxidations,
in the alkylation of aromatic compds, in the isomerization of conjugated
diolefins.