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elements – it belongs to the halogen family of five elements. These halogens also include fluorine, chlorine, iodine and the rapidly decaying radioactive element called astatine.

    Bromine—Part 1
    Bromine is one of the 92 or so elements. It belongs to the halogen family of five elements, which also includes fluorine, chlorine, iodine and the rapidly decaying radioactive element called astatine.
    The word ‘halogen’ comes from the Greek root hal , meaning ‘salt’, and gen , meaning ‘to produce’, because they all produce sodium salts which are very similar. The best known sodium salt is sodium chloride—common table salt.
    There is a difference between ‘bromine’ and ‘bromide’. ‘Bromine’ is the pure naked element. A ‘bromide’ is the compound you get when you combine the element bromine with another element, or a group of elements. (In a similar way, ‘chlorine’ is an element, while ‘sodium chloride’ is the compound produced when sodium and chlorine have been combined.)
    In general, halogens are very reactive, and tend to form strong acids such as HCl (hydrochloric acid) and HF (hydrofluoric acid). Hydrofluoric acid is so reactive that it will react with microscopic quantities of water in glass and actually eat the glass. For this reason, it has to be stored in special water-free glass, or containers lined with beeswax or Teflon™, or containers made of metals that immediately form a layer of inert fluoride (such as copper or steel).
    Bromine is, apart from mercury, the only element that is a liquid at room temperature. It is a deep red, fuming liquid with a reddish-brown, acrid poisonous gas. As a liquid it is toxic and causes flesh burns. Some bromine compounds can cause damage to the ozone layer, and are therefore being phased out of production.
    Bromine—Part 2
    Bromine was discovered independently by two chemists.
    In 1825, the chemist Carl Jacob Löwig separated bromine from a natural spring in his home town of Bad Kreuznach in Germany. In 1826, the French chemist Antoine-Jérôme Balard isolated bromine from the residues left in sea salt, after sea water had been evaporated. Bromine occurs at a low level in sea water, approximately 0.06-0.07 g per litre. (In the Dead Sea, the concentration is over 100 times greater—about 5 g per litre.)
    Balard published his results first, and so got all the credit. The French Academy of Sciences gave this element the name ‘bromine’ from the Greek word bromos , meaning ‘bad or pungent odour’ or ‘stench of goats’.
    Current world production of bromine is about 550,000 tonnes each year. Between 1928 and 1975, most bromine was used to make ethylene dibromide, which was added to the leaded petrols of the day to remove lead deposits from the inside of engine cylinders. Today, ethylene dibromide is used as a pesticide.
    Bromine is also used in fire retardants and to make various dyes, while silver bromide is used to make photographic film (the stuff they used before digital cameras). Bromine was used in the printing industry, and so the word ‘bromide’ can also mean ‘a reproduction or piece of typesetting on bromide paper’. And tiny amounts of potassium bromate improve the baking characteristics of wheat flour.
    Bromine—The Sedative
    The bromides of lithium, sodium, potassium, calcium, strontium and ammonium have also long been used in medicine because of their sedative effect. This could perhaps be the origin of thebromide myth. In the 19th century, these salts of bromine were used as sedatives to treat everything from mild difficulty in falling asleep to full-blown epilepsy. The dose was somewhere between 0.3 and 2 g, and given several times a day, to ‘reduce the excitability of the brain’. Indeed, another meaning for the word ‘bromide’ is ‘a trite or unoriginal idea or remark, typically intended to soothe or placate’, in other words, bromides create the illusion of wellbeing.
    In fact, in the 19th century, children of