A picrate is a salt containing the anion (O2N)3C6H2O− or an ester derivative of the picrate anion. These salts are often produced by reactions of picric acid (2,4,6-trinitrophenol). The picrate ion is intensely yellow.
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. 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.
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.
Ethers and esters
Ethers and esters of picric acid are also called picrates. The ether methyl picrate (CAS# 606-35-9) has the formula (O2N)3C6H2OCH3.
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