This International Standard specifies a method for the determination of the bromine number of the following materials: a) petroleum distillates that are substantially free of material lighter than 2-methylpropane, and that have 90 %(V/V) (i.e. volume fraction 90 %) distillation recovery temperatures under 327 °C. The method is generally applicable to gasolines (including leaded, unleaded and oxygenated fuels), kerosines and distillates in the gas oil range that fall within the following limits: 90 %(V/V) recovery distillation temperature (ISO 3405) Bromine number, max. (see note 1) Under 205 °C 175 205 °C to 327 °C 10 b) commercial olefins that are essentially mixtures of aliphatic monoolefins and that fall within the range of 95 to 165 bromine number (see note 1). The method has been found suitable for such materials as commercial propene trimer and tetramer, butene dimer, and mixed nonenes, octenes and heptenes. The method is not suitable for normal alpha-olefins. NOTES 1 These limits are imposed since the precision of the method has been determined only up to or within the range of these bromine numbers. 2 The value of the bromine number is an indication of the quantity of bromine-reactive constituents, not an identification of constituents. Annex A and table A.1 give information related to the use of this International Standard as a measure of olefinic unsaturation.