PYROGALLOL, or PYROGALLIC ACID, a trioxybenzene, C6HI(OH)3 (1: 2: 3), prepared by Scheele in 1786 by heating gallic acid, C6H2(OH)3COIH. It is also
obtained by heating para-chiorphenoldisuiphonic acid with potassium hydroxide.
It forms white plates, melting at 132, readily soluble in water, and subliming without decomposition. It is an energetic reducing agent, a propert3s
utilized in its application in gas analysis to absorb oxygen, and in photography (q.v.) as a developer. The aqueous solution is turned bluish black by
ferrous sulphate containing a ferric salt. It does not combine with hydroxylamine, as does the isomeric phlorogiucin which yields a trioxime(see
POLYMETnYLENES). Pyrogallol dimethyl ether is found in beechwood tar. Pyrogallol has antiseptic properties and is employed medicinally in the
treatment of psoriasis. Eugallol, or monacetyl pyrogallol and lenigallet~ or triacetyl pyrogallol, are also used.
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