Pyrogallol
Overview
Benzenetriol
Benzenetriols or trihydroxybenzenes are aromatic chemical compounds and polyphenols in which three hydroxyl groups are substituted onto a benzene ring....
. It is a white crystalline powder and a powerful reducing agent. It was first prepared by Scheele
Carl Wilhelm Scheele
Carl Wilhelm Scheele was a German-Swedish pharmaceutical chemist. Isaac Asimov called him "hard-luck Scheele" because he made a number of chemical discoveries before others who are generally given the credit...
1786 by heating gallic acid
Gallic acid
Gallic acid is a trihydroxybenzoic acid, a type of phenolic acid, a type of organic acid, also known as 3,4,5-trihydroxybenzoic acid, found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and other plants. The chemical formula is C6H23COOH. Gallic acid is found both free and as part of...
. An alternate preparation is heating para-chlorophenoldisulphonic acid with potassium hydroxide
Potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula KOH, commonly called caustic potash.Along with sodium hydroxide , this colorless solid is a prototypical strong base. It has many industrial and niche applications. Most applications exploit its reactivity toward acids and its corrosive...
.
When in alkaline solution, it absorbs oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
from the air, turning purple from a colourless solution. It can be used in this way to calculate the amount of oxygen in air, notably via the use of the Orsat apparatus.
One can find its uses in hair dying, dying of suturing materials and for oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
absorption in gas analysis.
