Bromine is the less reactive than Chlorine, but more than Iodine. This
element is obtained from seawater, which contains Bromide ions, and is oxidised
by Chlorine. However, in the laboratory Bromine can be prepared by the reaction
of a halide salt with sulphuric acid. This produces hydrogen bromide which can
be oxidized by manganese (IV) oxide to produce Bromine.
Test for Bromine:
One test for Bromine is based upon its oxidizing characterisitcs. Bromine
is a bleach. Used on moist litmus paper, it reacts making the latter go
completely colourless even though this reaction is rather slow.
Bromine is more reactive than iodine. If it is reacted with an iodide in
an aqueous solution, the latter darkens. Cyclohexane may be added in order
to show for the presence of Iodine by turning the solution purple.
When silver nitrate is added to bromine, it forms an insoluble compound.
Therefore, if bromine is present a pale yellow precipitate is formed in this
reaction.
Uses of Bromine:
Manufacture of 1,2-dibromoethane: Most of the bromine in the world
is used to produce this compound. It is added to leaded petrol to help
reduce the build-up of lead oxide in the engine, substance which is
hazarduous.
Manufacture of anitfreeze and hydraulic fluid: In the production of
these substances, bromine is used in one intermediate reaction to make
ethane-1,2-diol. This substance is then used to produce antifreeze and
hydraulic fluids.
Other uses: Bromine is also used to make pesticides, flame
retardants and is also widely used in photography.
