noun. A biologically important phenol, C₆H₆O₂, having two hydroxyl groups attached to the benzene ring, used in dyeing, tanning, photography, and as an antiseptic.

noun. A white crystalline substance, C₆H₄(OH)₂; orthodihydroxybenzene. It occurs in the urine of horses as pyrocatechol-sulphuric acid, and also in human urine and in some plants. It is made by fusing phenol, bromphenol, etc., with caustic potash and by the dry distillation of catechin and many tannins; it melts at 104° C. Also called pyrocatechin, pyrocatechinol, oxyphenic acid; and catechol.

noun. A dihydric phenol, benzene-1,2-diol, present in some tars.

"The products are phenol and pyrocatechol, with some quantity of an amorphous product probably formed by condensation of a quinone with the phenolic products of reaction."

catechol