A picrate is a salt or an ester of picric acid (a 2,4,6-trinitrophenol). But it could also be an additional compound which picric acid forms with many aromatic hydrocarbons, aromatic amines, aliphatic amines, alkalines, and other compounds. These additional compounds are also called picrates even though they are not a salt of picric acid.
The picrate ion has yellow color. Many picrates are explosives, for example ammonium picrate (known as Dunnite). Some are used as primary explosives, namely lead picrate or potassium picrate which find their use as primers for cartridge ammunition.
Sodium picrate is used as an etchant in metallography to differ preeutectoid ferrite in hypoeutectoid steel from preeutectoid cementite in hypereutectoid steel by etching cementite to a dark colour, whereas not attacking ferrite and thus it remains reflective.
Picrates of some metals tend to be significantly more sensitive to impact, friction and shock than picric acid itself. As a result, storage of picric acid (or mixtures containing it) in metal containers is strongly discouraged due to the high risk of accidental explosion.
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