A dicarboxylic acid, maleic acid is an organic compound used primarily as a precursor material for fumaric acid and maleic anhydride. It is derived industrially via hydrolysis of maleic anhydride, a substance synthesized by oxidizing benzene or butane. Much of the industrially produced maleic acid in the world is used as a raw material for manufacturing glyoxylic acid via ozonolysis. Additionally, maleic acid is sometimes implemented to form acid additions salts in combination with certain drugs in order to increase their overall stability (e.g. indacaterol maleate). It is further used in various applications as an adhesion promoter for substrates such as nylon and zinc coated metals such as galvanized steel, and also in methyl methacrylate adhesives. The vast majority of maleic acid produced around the world, however, is used in the isomerization process to convert it to fumaric acid. The most efficient process for this isomerization is to heat maleic acid or expose it to intense light.