Hydrogen bromide is a chemical compound. It dissolves in water to produce hydrobromic acid. Its chemical formula is HBr. It is a stinky colorless gas. It is used to make other bromides. It is made by reacting hot hydrogen and bromine with a catalyst. It can be made by reacting bromides with non-oxidizing acids, such as phosphoric acid. Bromine can be reduced by phosphorous acid to make hydrogen bromide.