Pyrogallol

Pyrogallol or benzene-1,2,3-triol is a white crystalline powder and a powerful reducing agent. It was first prepared by Scheele 1786 by heating gallic acid. An alternate preparation is heating para-chlorophenoldisulphonic acid with potassium hydroxide.

When in alkaline solution, it absorbs water readily, turning purple from a colourless solution. It can also absorb oxygen and is used to calculate the amount of oxygen in air.

One can find its uses in photography as developing agent, hair dying, dying of suturing materials and for oxygen absorption in gas analysis. It also has antiseptic properties.

Limited exposure to this compound is recommended. Pyrogallol is not likely to be used as a modern hair dye due to the suspected toxicity of the compound.