Bromine, symbolized as Br and having atomic number 35, is a member of the halogen group of elements. It is distinguished from most other non-metals because it exists as a volatile, dense liquid at room temperature. This element is characterized by its reddish-brown color and a strong, pungent odor, which is the source of its Greek-derived name, meaning “stench.” Bromine is highly reactive and is never found in its pure, elemental form in nature, instead occurring bound within various inorganic compounds called bromides. These unique properties dictate where and in what form the element is concentrated across the planet.
Primary Natural Sources
The overwhelming majority of bromine on Earth is dissolved as bromide ions in the hydrosphere, making the world’s oceans its largest natural reservoir. Seawater contains bromine at a relatively low concentration, typically around 65 parts per million (ppm). This vast volume of ocean water, however, represents an estimated reserve of over 100 trillion tons of the element.
Significantly higher concentrations are found in continental brine deposits and inland seas, which makes these sites the most commercially viable for extraction. Deep underground brine wells, often associated with oil and gas deposits, can contain bromine concentrations far exceeding those of the open ocean. The Dead Sea, for instance, is estimated to hold over one billion tons of bromine, with concentrations reaching 12,000 ppm.
Subterranean brine areas in the United States, particularly in Arkansas, also exhibit high bromide content, sometimes soaring to 7 grams per liter. These concentrated natural solutions are essentially the mother liquors left behind after the evaporation and crystallization of less soluble salts like sodium chloride. These highly concentrated aqueous sources represent the primary locations of natural abundance.
Industrial Production and Key Applications
The element is extracted from concentrated brines through a process that converts the dissolved bromide ions into elemental bromine. This is typically achieved by using a displacement reaction, where the brine is treated with an oxidizing agent, such as chlorine gas. The chlorine displaces the bromide from the solution, producing liquid bromine, which can then be isolated and purified.
Once extracted, bromine is channeled into a diverse range of industrial applications. The largest single commercial use is in the production of brominated flame retardants (BFRs), which are incorporated into plastics, textiles, and electronic casings. These compounds work by releasing bromine atoms when heated, which interrupts the radical chain reactions that characterize combustion.
Another significant industrial location for bromine is in clear brine fluids, which are highly saturated solutions used in oil and gas exploration and drilling. Bromine compounds also serve as intermediates in the synthesis of specialized organic chemicals, including pharmaceuticals and agricultural chemicals. Historically, specific brominated compounds were used as fumigants and pesticides, though many of these applications are now restricted due to environmental concerns.
Presence in the Environment and Biology
Bromine compounds eventually circulate into the wider environment as a result of both natural processes and the breakdown of manufactured products. Organobromine compounds can be found in the atmosphere, soil, and fresh water, often originating from the disposal or degradation of industrial flame retardants. Volatile organobromine compounds in the atmosphere can be broken down by ultraviolet sunlight, releasing free bromine atoms. This process contributes to the chemical reactions that deplete the stratospheric ozone layer.
Within living systems, bromine is present in trace amounts and has been identified as an essential trace element for all animals. Research indicates that the bromide ion is required to enable a specific enzyme to link collagen molecules. This function is fundamental to forming the structural scaffolding of cell tissue and supports the development of basement membranes throughout the animal kingdom.
In the human body, bromine is distributed across various tissues, with some research suggesting it may be concentrated in organs like the thyroid gland and kidneys. Marine organisms, such as red algae, are known to produce hundreds of natural organobromine compounds as part of their metabolic processes. The presence of bromine in the body and its involvement in structural tissue development illustrate that the element is not only an industrial commodity but also a component of life itself.