Pyrogallol /(?)/

Pyr·o·gal·lol

Pyrogallol

n.
  1. A phenol metameric with phloroglucin, obtained by the distillation of gallic acid as a poisonous white crystalline substance having acid properties, and hence called also pyrogallic acid. It is a strong reducer, and is used as a developer in photography and in the production of certain dyes. (Chem.)