- a colorless, crystalline, dihydroxyl derivative of benzene, C6H6O2, the ortho isomer, used chiefly in photography, for dyeing, and as a reagent; pyrocatechol.
- a colourless crystalline phenol found in resins and lignins; 1,2-dihydroxybenzene. It is used as a photographic developer. Formula: C 6 H 4 (OH) 2
