It is based on the following reaction: : Bromine is deeply colored but is not. Thus, the consumption of bromine can often be gauged visually. Alternatively and more quantitatively, the bromine consumed by a sample can be determined by
iodometry. The bromine number indicates the
degree of unsaturation of a sample. The technique can be subject to a variety of problems, whereby the sample consumes more or less bromine than predicted by the equation above. For example, some alkenes dimerize in the presence of bromine. Allylic bromination is another problem. found in petroleum-derived samples. The C=C double bonds in fats and fatty acids are exclusively disubstituted. The bromine number is usually determined by electrochemical
titration, where bromine is generated
in situ with the
redox process of
potassium bromide and
bromate in an acidic solution, using a mercury
catalyst to ensure the complete bromination of all olefins. ==Related test methods==