Picric acid
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218336999
2008-06-10T04:58:07Z
Puppy8800
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iw
:''"TNP" redirects here. For the airport with the IATA airport code TNP, see [[Twentynine Palms Airport]].
{{chembox new
| ImageFile1 = Pikrinsäure.svg
| ImageSize1 = 150px
| ImageFileL2 = 246trinitrophenol-3D-ball.png
| ImageSizeL2 = 100px
| ImageFileR2 = 246trinitrophenol-3D-vdW.png
| ImageSizeR2 = 100px
| IUPACName = 2,4,6-Trinitrophenol
| OtherNames = Carbazotic Acid; phenol trinitrate; picronitric acid; trinitrophenol; 2,4,6-trinitro-1-phenol; 2-hydroxy-1,3,5-trinitrobenzene; TNP
| Section1 = {{Chembox Identifiers
| Abbreviations =
| CASNo = 88-89-1
| EINECS =
| PubChem =
| SMILES = O=[N+]([O-])c1cc(cc([N+]([O-])=O)c1O)[N+]([O-])=O
| InChI =
| RTECS =TJ7875000
| MeSHName =
| ChEBI =
| KEGG =
| ATCCode_prefix =
| ATCCode_suffix =
| ATC_Supplemental =}}
| Section2 = {{Chembox Properties
| Formula = C<sub>6</sub>H<sub>3</sub>N<sub>3</sub>O<sub>7</sub>
| MolarMass =229.10 g/mol
| Appearance =Colorless to yellow solid
| Density = 1.763 g/cm³, solid
| MeltingPt = 122.5 °C
| Melting_notes =
| BoilingPt = > 300 °C
| Boiling_notes = Explodes
| Solubility = 1.40 g/100 mL
| SolubleOther =
| Solvent =
| pKa = 0.38
| pKb = }}
| Section7 = {{Chembox Hazards
| EUClass =
| EUIndex =
| MainHazards =
| NFPA-H = 3
| NFPA-F = 3
| NFPA-R = 4
| NFPA-O =
| RPhrases = {{R1}} {{R10}} {{R36}} {{R37}} {{R38}}
| SPhrases = {{S28}} {{S35}} {{S37}} {{S45}}
| RSPhrases =
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| Autoignition =
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| PEL = }}
| Section8 = {{Chembox Explosive
| ShockSens =
| FrictionSens =
| ExplosiveV = 7,350 m/s at ρ 1.70
| REFactor = }}
}}
'''Picric acid''' is the [[chemical compound]] more formally called 2,4,6-trinitrophenol (TNP). This, a yellow [[crystalline]] solid, is one of the most [[acid]]ic [[phenol]]s. Like other highly [[nitrate]]d compounds such as [[trinitrotoluene|TNT]], picric acid is an [[Explosive material|explosive]]. Its name comes from Greek πικρος—"bitter", reflecting the bitter taste of picric acid.
== History ==
Picric acid was probably first mentioned in the [[alchemical]] writings of [[Johann Rudolf Glauber]] in 1742. Initially, it was made by [[nitrating]] substances such as animal horn, [[silk]], [[indigo]], and natural [[resin]]. Its synthesis from [[phenol]], and the correct determination of its formula, were successfully accomplished in 1841. Not until 1830 did chemists think to use picric acid as an [[Explosive material|explosive]]. Before then, chemists assumed that only the [[salts]] of picric acid were [[Explosive material|explosive]], not the acid itself. In 1873 [[Hermann Sprengel]] proved it could be detonated and by 1894 the Russian workers had worked out a method of manufacture for artillery shells. Soon after, most [[military]] powers used picric acid as their primary high [[explosive material]]. However, shells filled with picric acid become highly unstable as the compound corrodes bomb casings to form metal [[picrate]]s which are more sensitive than the parent phenol. The sensitivity of picric acid was demonstrated in the [[Halifax Explosion]]. Picric was used in World War I <ref>Marc Ferro. ''The Great War''. London and New York: Routeladge Classics, p. 98.</ref>, but the 20th century saw picric acid largely replaced by [[Trinitrotoluene|TNT]]. Picric acid is also used in the analytical chemistry of metals, ores, and minerals.
In 1885, based on research of Hermann Sprengel, French chemist [[Eugène Turpin]] patented the use of pressed and cast picric acid in [[blasting]] charges and [[artillery shell]]s. In 1887 the French government adopted it under the name '''melinite''', with addition of [[nitrocellulose|gun cotton]]. Since 1888, Britain started manufacturing a very similar mixture in [[Lydd]], Kent, under the name '''lyddite'''. Japan followed with an improved formula known as '''schimose'''. In 1889, a similar material, a mixture of [[ammonium cresylate]] with [[trinitrocresol]], or an ammonium salt of trinitrocresol, started to be manufactured under the name '''[[ecrasite]]'''.
== Synthesis ==
The aromatic ring of [[phenol]] is highly activated towards electrophilic reactions, and attempted nitration of phenol, even with dilute nitric acid, results in the formation of high molecular weight tars. In order to minimize these side reactions, anhydrous phenol is sulphonated with [[oleum]], and the resulting "sulphophenol" is then nitrated with concentrated [[nitric acid]]. During this reaction, nitro groups are introduced, and sulfonic acid groups are displaced. The reaction is highly exothermic, and careful temperature control is required.
== Uses ==
By far the largest use has been in [[ammunition|munitions]] and explosives, as discussed above.
In [[microscopy]], picric acid is a reagent for staining samples, e.g. [[Gram staining]]. It has found some use in organic chemistry for the preparation of crystalline salts of organic bases (picrates) for the purpose of identification and characterization.
[[Bouin's picro-formol]] is a preservative solution used for biological specimens.
Workplace drug testing utilizes picric acid for the Jaffe Reaction to test for creatinine. It forms a colored complex that can be measured using spectroscopy.
Much less commonly, wet picric acid has been used as a skin dye or temporary branding agent. It reacts with proteins in the skin to give a dark brown color that may last as long as a month.
In the early 20th century, picric acid was stocked in pharmacies as an [[antiseptic]] and as a treatment for [[burns]], [[malaria]], [[herpes]], and [[smallpox]].
==Safety==
Modern safety precautions recommend storing picric acid wet. Dry picric acid is relatively sensitive to [[Shock (mechanics)|shock]] and [[friction]], so laboratories that use it store it in bottles under a layer of [[water (molecule)|water]], rendering it safe. Glass or plastic bottles are required, as picric acid can easily form metal [[picrate]] [[salt]]s that are even more sensitive and hazardous than the acid itself. Industrially, picric acid is especially hazardous because it is volatile and slowly sublimes even at room temperature. Over time, the buildup of picrates on exposed metal surfaces can constitute a grave hazard.
In 2007, a [[bomb disposal|bomb squad]] removed a [[World War I]]-era bottle containing two ounces in [[Columbus, Wisconsin]].<ref>{{cite news | publisher = [[Associated Press]] | format = reprint | title = Old Sample of Acid Detonated in Wis. | date = 16 Apr 2007 | url = http://www.foxnews.com/wires/2007Apr16/0,4670,ExplosiveAcid,00.html}}</ref> In another 2007 incident, bomb squad detonated sample in [[Hayward, California]].<ref>{{cite news | title = Bomb Squad Detonates Acid At Hayward Lab | publisher = [[KTVU.com]] | date = 22 Aug 07 | url = http://www.ktvu.com/news/13951124/detail.html}}</ref> In 2008, bomb disposal experts removed and later detonated a 200 g (7 oz) found at the [[Marling School]] ([[Stroud, Gloucestershire]]) science department.<ref>{{cite news | title = School evacuated after chemical found | work= Stroud News and Journal | date = 23 April 08 | url = http://www.stroudnewsandjournal.co.uk/mostpopular.var.2219663.mostviewed.school_evacuated_after_chemical_found.php}}</ref>
<ref>{{cite news | title = 'Unsafe chemical' found in school | publisher = [[Press Association]] | date = 23 April 08 | url = http://ukpress.google.com/article/ALeqM5i5v_MSv8nvizeYAGlmkQB4DX-cag}}</ref> A 1-lb. bottle of the acid was removed and later detonated by the bomb squad from an old pharmacy [[Jerseyville, Illinois]].<ref>{{ cite news | title = 'Bomb Squad Removes Explosive: Container of Acid Found in Old Drugstore | work = [[The Telegraph (Alton)|The Alton Telegraph]] | date = 8 May 08 }}</ref>
==References==
{{Reflist}}
* Cooper, Paul W., ''Explosives Engineering'', New York: Wiley-VCH, 1996. ISBN 0-471-18636-8
== External links ==
* [http://ptcl.chem.ox.ac.uk/MSDS/PI/picric_acid.html Safety Information]
[[Category:Explosive chemicals]]
[[Category:Nitro compounds]]
[[Category:Phenols]]
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