This test method is a good general means for measuring ethylenic (double-bond) unsaturation and is applicable to many compounds because of its speed, convenience, and minimum tendency for substitution. This test method has been applied to alpha-olefins, cyclic unsaturated hydrocarbons such as the cyclopentenes, unsaturated aliphatic side chains on aromatic rings, unsaturated esters and alcohols, acrylic and methyacrylic esters, acids, and salts, and other similar compounds. Diisobutylene and some tertiary-substituted hydrocarbons substitute to some extent but probably less by this test method than by most others. It is not satisfactory for such materials as commercial propylene trimer and tetramer, butene dimer, and mixed nonenes, octenes, and heptenes. For the bromine number of petroleum distillates that are substantially free of material lighter than isobutane and that have 90 % distillation points under 620°F (327°C) (such as gasoline), Test Method D 1159, is recommended.