# Picrate

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{{Short description|Salts and esters of picric acid}}
thumb|right|upright|Chemical structure of the picrate anion
A '''picrate''' is a [salt](/source/salt_(chemistry)) containing the anion (O<sub>2</sub>N)<sub>3</sub>C<sub>6</sub>H<sub>2</sub>O<sup>−</sup> or an [ester](/source/ester) derivative of the picrate anion.  These salts are often produced by reactions of [picric acid](/source/picric_acid) (2,4,6-trinitrophenol).<ref>{{cite journal|title=The picrate anion as a versatile chelating counterion for the complexation of alkali and alkaline earth metal cations with ionophores: 'the picrate effect'|author1=Olsher, Uriel |author2=Feinberg, Hadar |author3=Frolow, Felix |author4=Shoham, Gil |journal=Pure and Applied Chemistry|year=1996|volume=68|issue=6 |pages=1195–1199|doi=10.1351/pac199668061195|s2cid=96529554 |doi-access=free}}</ref><ref name=March>
{{cite book
  |author1=Smith, M. B. |author2=March, J. | title = March's Advanced Organic Chemistry
  | publisher = John Wiley & Sons
  | year = 2007|edition=6th
  | page = 118  
  | isbn =  978-0-471-72091-1}}</ref> The picrate ion is intensely yellow, although many of its salts are brown or orange-red.

==Explosives==
Many picrates are [explosive](/source/explosive)s, for example [ammonium picrate](/source/ammonium_picrate) (known as [Dunnite](/source/Dunnite)). Some are used as primary explosives, namely [lead picrate](/source/lead_picrate) or [potassium picrate](/source/potassium_picrate) which find their use as [primers](/source/Percussion_cap) for cartridge [ammunition](/source/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.

==Other uses==
[Ferrous picrate](/source/Ferrous_picrate) is used in some applications as a diesel [fuel additive](/source/fuel_additive) to achieve better [mileage](/source/Fuel_economy_in_automobiles).<ref>{{cite journal |doi=10.1016/j.apenergy.2011.09.007 |title=Effect of a homogeneous combustion catalyst on the combustion characteristics and fuel efficiency in a diesel engine |year=2012 |last1=Zhu |first1=Mingming |last2=Ma |first2=Yu |last3=Zhang |first3=Dongke |journal=Applied Energy |volume=91 |pages=166–172 }}</ref>

Sodium picrate is used as an etchant in [metallography](/source/metallography) to differ preeutectoid [ferrite](/source/Allotropes_of_iron) in hypoeutectoid steel from preeutectoid [cementite](/source/cementite) in hypereutectoid steel by [etching](/source/etching) cementite to a dark colour, whereas not attacking ferrite and thus it remains reflective.

Ethers and esters of picric acid are also called picrates.  The ether methyl picrate (CAS# 606-35-9) has the formula (O<sub>2</sub>N)<sub>3</sub>C<sub>6</sub>H<sub>2</sub>OCH<sub>3</sub>.

== References ==
{{Reflist}}

Category:Picrates

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