Adipic acid or hexane dioic acid is the organic compound with the formula (CH2)4(COOH)2. Adipic acid otherwise rarely occurs in nature, but it is known as manufactured E number food additive E355. Adipic acid has been incorporated into controlled-release formulation matrix tablets to obtain pH-independent release for both weakly basic and weakly acidic drugs. significant amounts of adipic acid are used as a food ingredient as a flavorant and gelling aid.