Hydrogen Bromide

hydrogen bromide [′hī·drə·jən ′brō‚mīd]

(inorganic chemistry)

HBr A hazardous, toxic gas used as a chemical intermediate and as an alkylation catalyst; forms hydrobromic acid in aqueous solution.

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Hydrogen Bromide 

(HBr), a compound of hydrogen and bromine. It is a colorless gas with a sharp odor and acidic taste; T_b = -68.7° C, T_m = -87.9° C. At 10° C approximately 350 volumes of hydrogen bromide dissolves in 1 volume of water. An aqueous solution of hydrogen bromide is called hydrobromic acid. This is a colorless liquid (sometimes yellowish owing to the presence of traces of bromine) with a sharp odor. An azeotropic mixture with a boiling point of 124.3° C forms at a concentration of 47.6 percent HBr.

Hydrobromic acid is one of the strongest mineral acids. In industry hydrogen bromide is obtained by the reaction of bromine vapors with hydrogen at a high temperature. The reaction temperature can be reduced by using a catalyst, activated charcoal, or platinized asbestos. Hydrogen bromide can be obtained in the laboratory by treating bromides with 50-percent sulfuric acid (more concentrated acid partially oxidizes HBr to Br₂) and by other methods. Hydrogen bromide is used to obtain bromides and organic bromine derivatives and for other purposes.