[mass noun] An acid extracted from oak galls and other vegetable products, formerly used in making ink.
- ‘The paper was then treated with gallic acid and then silver nitrate again.’
- ‘Pyrogallol, tannic acid, and gallic acid were obtained from Zhunyi Reagents (Guizou, China).’
- ‘Then, the paper is floated on a mixture containing silver nitrate and gallic acid.’
- ‘Modern compositions use other unstable, albeit somewhat less hazardous, aromatic compounds such as gallic acid or the salts of aromatic acids including sodium salicylate and potassium benzoate.’
- ‘By washing the paper with a solution of gallic acid after the exposure, he produced a developed-out image.’
Late 18th century: gallic from Latin galla oak gall (see gall)+ -ic.