Determination of the bromine number in petroleum distillate according to ASTM D1159 with toluene as solvent

The bromine number indicates the degree of unsaturation and relies on the simple addition of bromine to the double bonds of alkenes. One mol of bromine is consumed for each mol of carbon-carbon double bond. The bromine number thus indicates the olefin content in petroleum products.
Normally, chlorinated solvents are used for the determination of the bromine number. In this Application Note, toluene is used instead. First, the petroleum distillate is dissolved in toluene. Then, 5 mL sample solution are diluted with solvent. Afterwards, the bromine number ist quickly and accurately determined by potentiometric titration using a double Pt-wire electrode and bromide-bromate solution as titrant.