pyrogallol (pī´rōgăl´ōl) or pyrogallic acid (–Ĭk), C6H6O3, white, crystalline, aromatic compound with a biting taste; it is poisonous. It melts at 133°C and boils at 309°C. In alkaline solution it is an active reducing agent. Pyrogallol is widely used in photographic developing and in the manufacture of some dyes. Chemically it is a phenol; its IUPAC name is 1,2,3-trihydroxybenzene.