Fumaric acid

It has also been used in film-coated pellet formulations as an acidifying agent and also to increase drug solubility. Fumaric acid is also used as a food additive at concentrations up to 3600 ppm, and as a therapeutic agent in the treatment of psoriasis and other skin disorders.

Reported uses

Table: Reported uses (ppm): (Flavor and Extract Manufacturers' Association) [Table#2022].

Fortifier in paper size resins, unsaturated polyester resins, and alkyd surface coating resins, miscellaneous applications, acidulant in gelatin desserts and dry beverage powders, chemical intermediate for plasticizers including dibutyl fumarate.

Industrial uses: Dispersing agent, Flavoring and nutrient, Binder, Other, Processing aids not otherwise specified, Monomers, Fixing agent (mordant), Filler.

Consumer uses: Flavoring and nutrient, Dispersing agent.

The maleic acid concentration should be at least 30%. Maleic acid is converted almost quantitatively by thermal or catalytic isomerization into the sparingly soluble fumaric acid, which is recovered by filtration. Various substances have been proposed as catalysts: mineral acids (e.g., hydrochloric acid), sulfur compounds such as thiocyanates, thiazoles, thiosemicarbazides, thioureas, or bromine compounds in combination with peroxides (e.g., persulfate). Thiourea is most commonly used in practice. The maleic acid-containing wash water contains impurities that can affect quality and yield. This problem can be largely avoided (1) by thermal pretreatment of the wash water, (2) by adding urea if thiourea is used as catalyst, and (3) by addition of sulfites or passaged of sulfur dioxide and addition of mineral acids.