Nomenclature
CAS number: 7726-95-6
Description and references
Br; at. wt 79.904; at. no. 35; valences 1,
3, 5, 7. A halogen; Group VIIA (17). Does not exist as elemental
state, Br, in nature. Occurs as diatomic molecule, Br2. Abundance in igneous rock: 1.6 × 104% by wt; in seawater:
0.0065% by wt. Extracted commercially from natural brines (salt
lakes) and seawater. Naturally occurring stable isotopes (mass numbers):
79 (50.69%), 81 (49.31%); known artificial radioactive isotopes:
69-76, 77 (longest-lived known isotope, T 57.036 hr;
EC decay), 78, 79m, 80, 80m, 82-94. Discovery: A. J. Balard, Ann. Chim. Phys. 32, 337 (1826).
Books: Bromine and its Compounds, Z. E. Jolles, Ed. (E. Benn, London, 1966) 940 pp; Bromine Compounds: Chemistry and Applications, D. Price et al., Eds. (Elsevier, Amsterdam, 1988) 422
pp. Reviews: MTP Int. Rev. Sci.:
Inorg. Chem., Ser. One vol. 3, V. Gutmann,
Ed. (Butterworths, London, 1972); A. J. Downs, C. J. Adams, “Chlorine,
Bromine, Iodine and Astatine” in Comprehensive
Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1107-1573; Chemistry of the Elements, N. N. Greenwood,
A. Earnshaw, Eds. (Pergamon Press, New York, 1984) pp 920-1041; P.
F. Jackish in Kirk-Othmer Encyclopedia of
Chemical Technology vol. 4 (Wiley-Interscience,
New York, 4th ed., 1992) pp 536-560.
Properties
Dark reddish-brown, volatile, mobile, diatomic
liquid; suffocating odor; vaporizes rapidly at room temp. Only nonmetallic
element liquid at standard conditions. Nonflammable, but may ignite
combustibles on contact. Poisonous, corrosive. mp 7.25° (265.90 K); bp 59.47° (JANAF
Thermochemical Tables); 58.78° (Mellor's
Suppl. II, Part I, “The Halogens”); d425 3.1023; crit temp: 315°;
crit pressure: 102 atm. Heat capacity at constant pressure (liq,
25°) 18.089 cal/mole deg: Hildenbrand et al., J. Am. Chem. Soc. 80, 4129 (1958).
Vapor pressure data: A. N. Nesmeyanov, Vapor
Pressure of the Chemical Elements, R. Gary, Ed. (Elsevier,
New York, 1963) pp 354-58. Total soly in water (25°): 0.2141 moles/l
with formation of 0.00115 moles/l of HOBr; freely sol in alc, ether,
CHCl3, CCl4, CS2, concd HCl, aq solns
of bromides. Oxidizing agent; less reactive than chlorine; E0 (aq) Br2/Br 1.065 V; dissociation
energy (25°): 46.072 kcal. Keep sealed or
glass-stoppered.Caution
Potential symptoms of overexposure
are dizziness, headache; lacrimation, epistaxis; coughing, feeling
of oppression, pulmonary edema and pneumonia; abdominal pain, diarrhea;
measle-like eruptions; direct contact may cause severe burns of eyes
and skin. See NIOSH Pocket Guide
to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 32. See also Patty's Industrial Hygiene
and Toxicology vol. 2B, G. D. Clayton, F. E.
Clayton, Eds. (Wiley-Interscience, New York, 4th ed., 1994) pp 4505-4513.Use
Manuf of organic and inorganic chemicals, such as
fuel additives, fire retardants, pesticides, oil well drilling fluids,
pharmaceuticals, dyestuffs. Brominating agent. In water disinfection;
as bleaching agent, surface disinfectant.