Definition of phthalic acid in US English:

phthalic acid


  • A crystalline acid derived from benzene, with two carboxylic acid groups attached to the benzene ring.

    Chemical formula: C₆H₄(COOH)₂; three isomers

    • ‘Capillaries were immersed in phthalic acid, which has an index of refraction that effectively eliminates optical refraction at the outer wall.’
    • ‘Alkyd is produced by condensation reactions between polycarboxylic acids and polyhydric alcohols - often phthalic acid or anhydride and glycerol.’
    • ‘A wide range of uses has been found for various phthalic acid esters, with the largest portion of these esters being used as plasticizing agents for polyvinyl chloride products.’


Mid 19th century: phthalic, shortening of naphthalic (see naphthalene).


phthalic acid

/ˌTHalik ˈasid/