Styphnic acid

Styphnic acid, or 2,4,6-trinitro-1,3-benzenediol, is a yellow astringent acid that forms hexagonal crystals. It is used in the manufacture of dyes, pigments, inks, medicines, and explosives such as lead styphnate. It is itself a sensitive explosive, similar to picric acid.

Preparation and chemistry
It may be prepared by the nitration of resorcinol with a mixture of nitric and sulfuric acid.

This compound is an example of a trinitro phenol.

Like picric acid, it is a moderately strong acid, displacing carbon dioxide from solutions of sodium carbonate for example.

It may be reacted with weakly basic oxides such as those of lead and silver to form the corresponding salts.

The solubility of picric acid and styphnic acid in water is far less than the non nitrated phenol and less than the corresponding mono and di nitro compounds so they may be purified by fractional crystallisation.