This visual indicator titration method is for determining maleic anhydride reactivity with a wide variety of oils ranging from debutanized light hydrocarbon distillates to heavy drying oils.

The method gives a measure of the conjugated diolefin content of the sample. The determination is somewhat empirical1 since some diolefins may not react completely, while certain compounds other than conjugated diolefins may be reactive, also. For example, anthracene, many of its homologs, and the corresponding alkylated compounds react quantitatively as dienes with maleic anhydride. Similarly, certain vinyl aromatics react. The molecular weight of the conjugated diolefins must either be known or estimated. Therefore, the results obtained by this method must be carefully interpreted in the light of these specified limitations.