The bromine number was once used as a measure of aliphatic unsaturation in gasoline and related petroleum samples, but this assay has fallen into disuse with the introduction of spectroscopic and chromatographic analyses.
Alternatively and more quantitatively, the bromine consumed by a sample can be determined by iodometry.
The technique can be subject to a variety of problems, whereby the sample consumes more or less bromine than predicted by the equation above.
Iodine is less reactive toward the tri- and tetra-substituted double bonds,[2] found in petroleum-derived samples.
The C=C double bonds in fats and fatty acids are exclusively disubstituted.