Picramic acid, also known as 2-amino-4,6-dinitrophenol, is an acid obtained by neutralizing an alcoholic solution of picric acid with ammonium hydroxide.
Picramic acid are used in hair colouring formulations. As the pKa of Picramic acid is around 4, it is always the picramate which is available in a typical hair dye formulation (pH 6.5- pH 10).
Sodium picramate, a non reactive dye, is used as a direct hair coloring in oxidative hair dye formulation. Sodium picramate is said to be stable under conditions used in oxidative formulations and does not take part on the oxidation coloring forming mechanism.