Pyrogallic acid

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Tiny, white, light-sensitive crystals that tend to float with air movement. Pyrogallic acid, or pyro, is used as a developer in photographic solutions. It reduces the salts of Gold, Silver, Mercury, and Platinum to their metallic state. This characteristic was first noted in 1832 and soon after it was applied to photograph development. Pyrogallic acid is also used in the manufacture of dyes.

Chemical structure

Pyrogallic acid.jpg

Synonyms and Related Terms

pyrogallol; pyro; 1,2,3-trihydroxybenzene; 1,2,3-benzenetriol; Fouramine brown AP; Fourrin; CI 76515; Oxidation base 32; Piral


  • Toxic by ingestion, inhalation and skin absorption.
  • Skin contact can cause irritation and allergies.
  • Combustible.
  • Fisher Scientific: SDS

Physical and Chemical Properties

Soluble in water, ethanol, ether. Needle-shaped crystals.

Composition C6H3(OH)3
CAS 87-66-1
Melting Point 131-134 C
Density 1.45g/ml
Molecular Weight mol. wt.=126.1
Boiling Point 309 C

Resources and Citations

  • Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 796
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993