A sealed vial of liquid bromine, encased in an acrylic cube, which is a common and secure way of presenting the chemical element for teaching purposes, as its vapors are corrosive and toxic. In nature, bromine exists exclusively as bromide salts in diffuse amounts in crustal rock. Organobromine compounds are used in a wide variety of products, including fire retardant, gasoline additives, pesticides, and anti-convulsant medicines. It has no known essential role in human or mammalian health.Photo: Alchemist-hp