Wikipedia

Picric acid

"Lyddite" redirects here. For the rock type, see Lydite. For the movement of English textile workers, see Luddite.
Picric acid
Names
Preferred IUPAC name
2,4,6-Trinitrophenol[1]
Systematic IUPAC name
2,4,6-Trinitrobenzenol
Other names
Picric acid[1]
Carbazotic acid
Phenol trinitrate
Picronitric acid
Trinitrophenol
2,4,6-Trinitro-1-phenol
2-Hydroxy-1,3,5-trinitrobenzene
TNP
Melinite
Lyddite
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.001.696 Edit this at Wikidata
RTECS number
  • TJ7875000
UNII
UN number UN1344
  • InChI=1S/C6H3N3O7/c10-6-4(8(13)14)1-3(7(11)12)2-5(6)9(15)16/h1-2,10H checkY
    Key: OXNIZHLAWKMVMX-UHFFFAOYSA-N checkY
  • InChI=1/C6H3N3O7/c10-6-4(8(13)14)1-3(7(11)12)2-5(6)9(15)16/h1-2,10H
    Key: OXNIZHLAWKMVMX-UHFFFAOYAM
  • O=[N+]([O-])c1cc(cc([N+]([O-])=O)c1O)[N+]([O-])=O
Properties
C6H3N3O7
Molar mass 229.104 g·mol−1
Appearance Colorless to yellow solid
Density 1.763 g/cm3, solid
Melting point 122.5 °C (252.5 °F; 395.6 K)[2]
Boiling point Sublimes above MP
12.7 g/L
Solubility in Sulfuric acid
  • 10.18 g/100g sln. (18 °C (64 °F; 291 K))
  • 16.23 g/100g sln. (50 °C (122 °F; 323 K))
  • 25.86 g/100g sln. (80 °C (176 °F; 353 K))
(in 100% H2SO4)[2]
Solubility in Ethanol 7.452 g/100g[2]
Solubility in Diethyl ether 1.08 g/100g (13 °C (55 °F; 286 K))[2]
Solubility in Benzene 5.9 g/100g (15 °C (59 °F; 288 K))[2]
Solubility in Toluene 12.0 g/100ml (20 °C (68 °F; 293 K))[2]
Solubility in Amyl alcohol 1.755 g/100ml (20 °C (68 °F; 293 K))[2]
log P 1.33[3]
Vapor pressure
  • 2 mmHg (0.27 kPa) (195 °C (383 °F; 468 K))
  • 50 mmHg (6.7 kPa) (255 °C (491 °F; 528 K))[2]
Acidity (pKa) 0.38
−84.34×10−6 cm3/mol
Structure[4]
Orthorhombic
Pca21
a = 9.2596 Å, b = 19.138 Å, c = 9.7075 Å
α = 90°, β = 90°, γ = 90°
1720.3 Å3
8
Thermochemistry[2]
−215 kJ/mol
Enthalpy of fusion (ΔfH⦵fus)
 20 kJ/mol
88 kJ/mol
Explosive data[2]
Shock sensitivity
  • 65–93 cm (26–37 in) (Bureau of Mines test)
  • 33 cm (13 in) (Picatinny Arsenal test)
  • 4 g (62 gr) rifle bullet at more than 400 m/s (1,300 ft/s)
Friction sensitivity Very slight (produces weak burning odor)
Detonation velocity 7,480 m/s (24,500 ft/s) at ρ=1.70
RE factor
  • 1.12 (Ballistic mortar test)
  • 1.01 (Trauzl test)
  • 1.07 (Plate dent test)
Hazards[3]
GHS labelling:
GHS01: ExplosiveGHS02: FlammableGHS06: Toxic
Danger
H228, H301+H311, H317, H332
P210, P240, P241, P261, P264, P270, P271, P272, P280, P301+P310+P330, P302+P352, P302+P352+P312, P304+P340+P312, P333+P313, P361, P363, P370+P378, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 4: Readily capable of detonation or explosive decomposition at normal temperatures and pressures. E.g. nitroglycerinSpecial hazards (white): no code
2
4
4
Flash point 150 °C; 302 °F; 423 K[5]
300–310 °C (572–590 °F; 573–583 K)[2] Burns after melting with sooty flame and characteristic whistling noise. (may explode if confined, contaminated with picrates, or in contact with metals that form picrates)
0.1 mg/m3 (TWA)
Lethal dose or concentration (LD, LC):
  • 100 mg/kg (guinea pig, oral)
  • 250 mg/kg (cat, oral)
  • 120 mg/kg (rabbit, oral)[6]
NIOSH (US health exposure limits):
PEL (Permissible)
 0.1 mg/m3 (TWA, skin)
REL (Recommended)
  • 0.1 mg/m3 (TWA)
  • 0.3 mg/m3 (ST, skin)[5]
IDLH (Immediate danger)
 75 mg/m3[5]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Picric acid is an organic compound with the formula (O2N)3C6H2OH. Its IUPAC name is 2,4,6-trinitrophenol (TNP). The name "picric" comes from Greek: πικρός (pikros), meaning "bitter", due to its bitter taste. It is one of the most acidic phenols. Like other strongly nitrated organic compounds, picric acid is an explosive, which is its primary use. It has also been used as medicine (antiseptic, burn treatments) and as a dye.

History

[edit]

Picric acid was probably first mentioned in the 17th-century alchemical writings of Johann Rudolf Glauber. Initially, it was made by nitrating substances such as animal horn, silk, indigo, and natural resin, the synthesis from indigo first being performed by Peter Woulfe in 1771.[7]

The German chemist Justus von Liebig had named picric acid Kohlenstickstoffsäure (rendered in French as acide carboazotique).[citation needed] Picric acid was given that name by the French chemist Jean-Baptiste Dumas in 1841.[8] Its synthesis from phenol, and the correct determination of its formula, were accomplished during 1841.[9] In 1799, French chemist Jean-Joseph Welter (1763–1852) produced picric acid by treating silk with nitric acid; he found that potassium picrate could explode.[10] Not until 1830 did chemists think to use picric acid as an explosive. Before then, chemists assumed that only the salts of picric acid were explosive, not the acid itself.[citation needed]

A theory to explain why picrate salts detonated whereas picric acid itself didn't, was proposed by the French chemists Antoine Fourcroy and Louis Vauquelin in 1806 and reiterated by the French chemist Michel Chevreul in 1809. Picric acid evidently contained enough oxygen within itself — i.e. it was "super-oxygenated" (suroxigéné) — to combust completely even in the absence of air (because even in the absence of air, heat could transform it completely into gases, leaving no carbon). However, when picric acid was burned, the heat that was generated caused some of the acid to evaporate, dissipating so much heat that only burning, not detonation, occurred. In contrast, picrate salts were solids that did not sublimate, thus did not dissipate heat; hence, they did detonate.[11][12]

In 1871 Hermann Sprengel proved it could be detonated at the gunpowder works of John Hall & Sons in Faversham in Kent, England. Sprengel filed patents in Britain for "safety explosives" (i.e., stable explosives) on April 6, 1871 (no. 921),[citation needed] and on October 5, 1871 (no. 2642); in the latter patent, Sprengel proposed using picric acid dissolved in nitric acid as an explosive.[citation needed][13][14][page needed] Afterwards most military powers used picric acid as their main high explosive material.[citation needed] A full synthesis was later found by Leonid Valerieovich Kozakov.[citation needed]

Picric acid was the first strongly explosive nitrated organic compound widely considered suitable to withstand the shock of firing in conventional artillery. Nitroglycerine and nitrocellulose (guncotton) were available earlier, but shock sensitivity sometimes caused detonation in an artillery barrel at the time of firing. 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 shells. [citation needed]

In 1887 the French government adopted a mixture of picric acid and guncotton with the name Melinite. In 1888, Britain started manufacturing a very similar mixture in Lydd, Kent, with the name Lyddite. Japan followed with an alternative stabilization approach known as Shimose powder which, instead of attempting to stabilize the material itself, removed its contact with metal by coating the inside of the shells with layer(s) of resin and wax.[15]

By 1894 Russia was manufacturing artillery shells filled with picric acid. However, shells filled with picric acid become unstable if the compound reacts with the metal shell or fuze casings to form metal picrates which are more sensitive than the parent phenol. The sensitivity of picric acid was demonstrated by the Halifax Explosion.[citation needed]

Workers filling shells with liquid melinite at a French munitions factory during WWI

Picric acid was used in the Battle of Omdurman, the Second Boer War, the Russo-Japanese War, and World War I.[16][17][18][19]

Germany began filling artillery shells with trinitrotoluene (TNT) in 1902. Toluene was less readily available than phenol, and TNT is slightly less powerful than picric acid, but the improved safety of munitions manufacturing and storage caused the replacement of picric acid by TNT for most military purposes between the World Wars.[16][page needed]

Efforts to control the availability of phenol, the precursor to picric acid, emphasize its importance in World War I. Germans are reported to have bought US supplies of phenol and converted it to acetylsalicylic acid (aspirin) to keep it from the Allies. At the time, phenol was obtained from coal as a co-product of coke ovens and the manufacture of gas for gas lighting. Laclede Gas reports being asked to expand production of phenol (and toluene) to assist the war effort.[20] Both Monsanto and Dow Chemical began manufacturing synthetic phenol in 1915, with Dow being the main producer.[21][22] Dow describes picric acid as "the main battlefield explosive used by the French. Large amounts [of phenol] also went to Japan, where it was made into picric acid sold to the Russians."[22]

Photograph showing the use of picric acid on a farm to remove stumps and rocks.

Synthesis

[edit]

The aromatic ring of phenol is activated towards electrophilic substitution 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 sulfonated with fuming sulfuric acid, and the resulting sulfonic acid is then nitrated with concentrated nitric acid. During this reaction, nitro groups are introduced, and the sulfonic acid group is displaced. The reaction is highly exothermic, and careful temperature control is required. Synthesis routes that nitrate aspirin or salicylic acid can also be used to mitigate tar formation. Carbon dioxide is lost from the former via decarboxylation, while both acetic acid and carbon dioxide are lost from the latter.[23][better source needed] Another method of picric acid synthesis is direct nitration of 2,4-dinitrophenol with nitric acid.[24][25]

Uses

[edit]

By far the greatest use of picric acid has been in ammunition and explosives.

Derivatives

[edit]

Ammonium picrate (Explosive D, also known as Dunnite), is the ammonium salt of picric acid. It is notably less sensitive to impact than either picric acid or TNT (16–17 in (41–43 cm) initiation drop height using the Picatinny Arsenal apparatus, vs. 12–14 in (30–36 cm) for TNT and 13 in (33 cm) for PA), which allowed its use in armor piercing ammunition. Ammonium picrate was used by the United States army beginning in 1901 and the navy in 1907.[2]

Picramide, formed by aminating picric acid (typically beginning with Dunnite), can be further aminated to produce the very stable explosive TATB.[citation needed] 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.[citation needed]

Optical metallography

[edit]

In metallurgy, a 4% picric acid in ethanol etch, termed "picral", has been commonly used in optical metallography to reveal prior austenite grain boundaries in ferritic steels. The hazards associated with picric acid have meant it has largely been replaced with other chemical etchants. However, it is still used to etch magnesium alloys, such as AZ31.[citation needed]

Histology

[edit]

Bouin solution is a common picric-acid–containing fixative solution used for histology specimens.[26] It improves the staining of acid dyes, but it can also result in hydrolysis of any DNA in the sample.[27]

Picric acid is used in the preparation of Picrosirius red, a histological stain for collagen.[28][29]

Blood tests

[edit]

Clinical chemistry laboratory testing utilizes picric acid for the Jaffe reaction to test for creatinine. It forms a colored complex that can be measured using spectroscopy.[30]

Picric acid forms red isopurpurate with hydrogen cyanide (HCN). By photometric measurement of the resulting dye, picric acid can be used to quantify hydrogen cyanide.[31]

During the early 20th century, picric acid was used to measure blood glucose levels. When glucose, picric acid and sodium carbonate are combined and heated, a characteristic red color forms. With a calibrating glucose solution, the red color can be used to measure the glucose levels added. This is known as the Lewis and Benedict method of measuring glucose.[32]

Skin dye

[edit]

Much less commonly, wet picric acid has been used as a skin dye, or temporary branding agent.[citation needed] It reacts with proteins in the skin to give a dark brown color that may last as long as a month.[citation needed]

Antiseptic

[edit]

During the early 20th century, picric acid was stocked in pharmacies as an antiseptic and as a treatment for burns, malaria, herpes, and smallpox. Picric-acid–soaked gauze was commonly stocked in first aid kits from that period as a burn treatment.[citation needed] It was notably used for the treatment of burns suffered by victims of the Hindenburg disaster in 1937.[citation needed]

Picric acid was used as a treatment for trench foot suffered by soldiers on the Western Front during World War I.[33]

Picric acid has been used for many years by fly tyers to dye mole skins and feathers a dark olive green for use as fishing lures. Its popularity has been tempered by its toxic nature.[citation needed]

Safety

[edit]

Modern safety precautions recommend storing picric acid wet, to minimize the danger of explosion. Glass or plastic bottles are required, as picric acid forms metal picrate salts that can be more sensitive and hazardous than the acid, and which are powerful enough to initiate detonation in the acid.[2] The buildup of picrates on exposed metal surfaces can constitute an explosion hazard.[34]

Picric acid gauze, if found in antique first aid kits, presents a safety hazard because picric acid of that vintage (60–90 years old) will have become crystallized and unstable, or it may have formed metal picrates from long storage in a metal first aid case.[35]

Bomb disposal units are often called to dispose of picric acid if it has dried out.[36][37] In the United States there was an effort to remove dried picric acid containers from high school laboratories during the 1980s.[citation needed]

Munitions containing picric acid may be found in sunken warships. The buildup of metal picrates over time renders them shock-sensitive and extremely hazardous. It is recommended that shipwrecks that contain such munitions not be disturbed. The hazard may subside when the shells become corroded enough to admit seawater as these materials are water-soluble.[38] There are fluorescent probes to detect picric acid in very minute quantities.[39]

See also

[edit]

References

[edit]
  1. ^ a b Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: Royal Society of Chemistry. 2014. p. 691. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ a b c d e f g h i j k l m Kaye, Seymour M. (1 January 1978). "P - Dinitrophenols - Picric Acid". Encyclopedia of Explosives and Related Items (PDF) (Technical report). Vol. 8, M1 Thickener through Pyruvonitrolic Acid. Dover, NJ: Army Armament Research And Development Center - Large Caliber Weapon Systems Lab. pp. P277, P286-9, P292-3. LCCN 61-61759. ADA057762, PATR 2700.
  3. ^ a b "SDS - Picric Acid" (PDF). www.chemimpex.com. ChemImpex. Retrieved 20 January 2026.
  4. ^ Sun, Yin-Xia; Ren, Zong-Li; Meng, Wei-Sheng (2013). "Supramolecular Structure of 2,4,6-Trinitrophenol". Asian Journal of Chemistry. 25 (11): 6186–6188. doi:10.14233/ajchem.2013.14306. Retrieved 20 January 2026.
  5. ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0515". National Institute for Occupational Safety and Health (NIOSH).
  6. ^ "Picric acid". Immediately Dangerous to Life or Health Concentrations. National Institute for Occupational Safety and Health.
  7. ^ Woulfe, Peter (31 December 1771). "XV. Experiments to shew the nature of Aurum mosaicum: By Mr. Peter Woulfe, F. R. S". Philosophical Transactions of the Royal Society of London (61): 127–130. doi:10.1098/rstl.1771.0015.
  8. ^ Dumas, J. (1841). "Quatrième mémoire sur les types chimiques" [Fourth memoir on chemical types]. Annales de Chimie et de Physique. 3rd series (in French). 2: 204–232. C'est sous ce nom que j'ai désigné l'acide carboazotique, ... [It is by this name [i.e., picric acid] that I designated carboazotic acid, ...]
  9. ^ Laurent, Auguste (1841). "Sur le phényle et ses dérivés" [On phenol and its derivatives]. Annales de Chimie et de Physique. 3. 3: 221–228.
  10. ^ Welter, Jean-Joseph (1799). "Sur quelques matières particulières, trouvées dans les substances animals, traitées par l'acide nitrique" [On some particular materials, found in animal substances, treated with nitric acid]. Annales de Chimie et de Physique. 1st series (in French). 29: 301–305. Le lendemain je trouvai la capsule tapisée de cristaux dorés qui avoient la finesse de la soie, qui détonoient comme la poudre à canon, et qui, à mon avis, en auroient produit l'effet dans une arme à feu. & ...je nommerai "amer". [The next day, I found the crucible covered with golden crystals which had the fineness of silk, which detonated like gun powder, and which, in my opinion, would produce the same effect in a firearm. & ...I will name it "bitter".]
  11. ^ Fourcroy; Vauquelin (1806). "Mémoire sur la découverte d'une nouvelle matière inflammable et détonnante, formée par l'action de l'acide nitrique sur l'indigo et les matières animales" [Memoir on the discovery of a new flammable and explosive substance, formed by the action of nitric acid on indigo and animal substances]. Mémoires de l'Institute des Sciences et Arts (in French). 6: 542–543.
  12. ^ Chevreul (1809). "Extrait d'un mémoire sur les substances amères formées par la réaction de l'acide nitrique sur l'indigo" [Extract from a memoir on the bitter substances formed by the reaction of nitric acid with indigo]. Annales de Chimie et de Physique (in French). 72: 127–30.
  13. ^ Sprengel, Hermann (1873). "XXXII.—On a new class of explosives which are non-explosive during their manufacture, storage, and transport". J. Chem. Soc. 26: 796–808. doi:10.1039/js8732600796.
  14. ^ Sprengel, Hermann (1903). The Discovery Of Picric Acid (Melinite, Lyddite) As A Powerful Explosive And Of Cumulative Detonation With Its Bearing On Wet Guncotton (2nd ed.). London: Eyre & Spottiswoode.
  15. ^ Koike, Shigeki (2006). "The Russo-Japanese War and the system of SHIMOSE gunpowder" (PDF). Bulletin of Papers (in Japanese). 1 (49). Takasaki City University of Economics. Archived (PDF) from the original on 5 March 2016. Retrieved 18 September 2020.
  16. ^ a b Brown, G.I. (1998). The big bang: a history of explosives. Stroud, UK: Sutton Pub. pp. 151–163. ISBN 0-7509-1878-0. OCLC 40348081.
  17. ^ Wisser, John Philip (1901). The second Boer War, 1899–1900. Hudson-Kimberly. p. 243. Retrieved 2009-07-22.
  18. ^ "Dunnite Smashes Strongest Armor" (PDF). The New York Times. 18 August 1907. Retrieved 20 January 2026.
  19. ^ Ferro, Marc (2002). The Great War, 1914-1918. London ; New York: Routledge. p. 98. ISBN 9780415267359.
  20. ^ Beck, Bill (2007). Laclede Gas and St. Louis: 150 Years of Working Together, 1857-2007. St. Louis: Laclede Gas Company. p. 64. ISBN 9780971091016.
  21. ^ Forrestal, Dan J. (1977). Faith, hope, and $5,000: the story of Monsanto: the trials and triumphs of the first 75 years. New York: Simon and Schuster. p. 24. ISBN 0-671-22784-X.
  22. ^ a b Brandt, E. N. (1997). Growth company: Dow Chemical's first century. East Lansing: Michigan State University Press. pp. 77, 97, 244. ISBN 0-87013-426-4.
  23. ^ "λ » LambdaSyn – Synthese von Pikrinsäure". www.lambdasyn.org (in German). Retrieved 2024-08-01.
  24. ^ Agrawal, Jai Prakash; Hodgson, Robert (2007-01-11). Organic Chemistry of Explosives. John Wiley & Sons. ISBN 9780470059357.
  25. ^ Green, Arthur George (1919-04-01). "Manufacture of picric acid. US Patent US1299171A". patents.google.com. Retrieved 2018-08-26.
  26. ^ Carson, Freida L.; Hladik, Christa (2009). Histotechnology: A Self-Instructional Text (3 ed.). Hong Kong: American Society for Clinical Pathology Press. p. 19. ISBN 978-0-89189-581-7.
  27. ^ Llewellyn, Brian D (February 2009). "Picric Acid". StainsFile. Archived from the original on 31 May 2015. Retrieved 28 September 2012.
  28. ^ Lattouf R, Younes R, Lutomski D, Naaman N, Goudeau G, Senni K, Changotade S (2014). "Picrosirius Red Staining: A Useful Tool to Appraise Collagen Networks in Normal and Pathological Tissues". Journal of Histochemistry & Cytochemistry. 62 (10): 751–758. doi:10.1369/0022155414545787. PMID 25023614.
  29. ^ Junqueira LC, Bignolas G, Brentani RR (1979). "Picrosirius staining plus polarization microscopy, a specific method for collagen detection in tissue sections". The Histochemical Journal. 11 (4): 447–455. doi:10.1007/BF01002772. PMID 91593.
  30. ^ "Creatinine Direct Procedure, on CimaScientific". Archived from the original on 2020-08-06. Retrieved 2011-03-26.
  31. ^ "Quantification of total cyanide content in stone fruit kernels" (PDF). Archived from the original (PDF) on 2019-04-30.
  32. ^ 2"Measuring blood glucose levels in the 1920s". Tacomed.com. Archived from the original on 16 December 2018. Retrieved 13 June 2017.
  33. ^ Macpherson, W.G.; Bowlsby, A.A.; Wallace, Cuthbert; English, Crisp, eds. (1922). History of the Great War - Surgery of the War. History of the great war based on official documents. Vol. 1. London: His Majesty's Stationery Office. p. 175.
  34. ^ "Picric Acid, Wet". hazard.com. 21 April 1998. Retrieved 13 April 2021.
  35. ^ Harding, Evan; Searle, Jamie (7 July 2021). "Potentially explosive substance was in Catlins museum for decades". Stuff. Retrieved 20 July 2021.
  36. ^ "Bomb squad called to Dublin lab". irishtimes.com. Irish Times. 1 October 2010. Archived from the original on 22 October 2012. Retrieved 22 July 2011.
  37. ^ "Unstable chemicals made safe by army". rte.ie. RTÉ News. 3 November 2010. Retrieved 22 July 2011.
  38. ^ Albright, Richard (2011). Cleanup of Chemical and Explosive Munitions: Location, Identification and Environmental Remediation. William Andrew. p. 78. doi:10.1016/C2010-0-67036-2. ISBN 978-1-4377-3477-5.
  39. ^ Arunkumar, Chellaiah; Sujatha, Subramaniam (26 Oct 2015). "Protonation and axial ligation intervened fluorescence turn-off sensing of picric acid in freebase and tin(iv) porphyrins". RSC Advances. 5 (113): 93243. Bibcode:2015RSCAd...593243S. doi:10.1039/C5RA18310C.