Pyrogallol is the oldest photographic developer, its rapid deposition of silver from silver salts having first been noted in 1832. Alkaline solutions of pyrogallol absorb oxygen efficiently and are used in determining the oxygen content of gas mixtures.
A hydrolyzable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids. ... Examples of gallotannins are the gallic acid esters of glucose in tannic acid (C76H52O46), found in the leaves and bark of many plant species.
One can find its uses in hair dyeing, dyeing of suturing materials and for oxygen absorption in gas analysis. It also has antiseptic properties. Pyrogallol was also used as a developing agent in black-and-white developers, but its use is largely historical except for special purpose applications.
Pyrogallol use, e.g. in hair dye formulations, is declining because of concerns about its toxicity.[8] Its LD50 (oral, rat) is 300 mg/kg.
