A flask containing bromine gas. Bromine is a fuming red-orange coloured liquid that boils at 59 Celsius. It has an atomic number of 35, the symbol Br and is a member of the halogens (group 17). In its elemental form it is diatomic with the formula Br2. It is highly corrosive and toxic, reacting readily with water to for hydrobromic acid. Its compounds are used in well drilling fluids, photographic films and in industrial organic chemistry.