Picric acid

Picric acid
Preferred IUPAC name
Other names
Picric acid[1]
Carbazotic acid
Phenol trinitrate
Picronitric acid
3D model (JSmol)
ECHA InfoCard100.001.696
RTECS numberTJ7875000
Molar mass229.10 g·mol−1
AppearanceColorless to yellow solid
Density1.763 g·cm−3, solid
Melting point 122.5 °C (252.5 °F; 395.6 K)
Boiling point> 300 °C (572 °F; 573 K) Detonates
12.7 g·L−1
Vapor pressure1 mmHg (195 °C)[2]
Acidity (pKa)0.38
-84.34·10−6 cm3/mol
Main hazardsexplosive
Toxic T Explosive E Extremely Flammable F+
R-phrases (outdated)R1 R4 R11 R23 R24 R25
S-phrases (outdated)S28 S35 S37 S45
NFPA 704
Flash point 150 °C; 302 °F; 423 K [2]
Lethal dose or concentration (LD, LC):
100 mg/kg (guinea pig, oral)
250 mg/kg (cat, oral)
120 mg/kg (rabbit, oral)[3]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 0.1 mg/m3 [skin]
REL (Recommended)
TWA 0.1 mg/m3 ST 0.3 mg/m3 [skin][2]
IDLH (Immediate danger)
75 mg/m3[2]
Explosive data
Detonation velocity7,350 m·s−1 at ρ 1.70
RE factor1.20
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

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 the Greek πικρός (pikros), meaning "bitter", reflecting its bitter taste. It is one of the most acidic phenols. Like other highly nitrated organic compounds, picric acid is an explosive, hence its primary use. It has also been used in medicine (antiseptic, burn treatments) and dyes.


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, the synthesis from indigo first being performed by Peter Woulfe in 1771.[4] Its synthesis from phenol, and the correct determination of its formula, were successfully accomplished in 1841.[5] 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. In 1871 Hermann Sprengel proved it could be detonated[6] and most military powers used picric acid as their main high explosive material. Picric acid is also used in the analytical chemistry of metals, ores, and minerals.

Picric acid was the first high 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 the 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. In 1887 the French government adopted a mixture of picric acid and guncotton under the name Melinite. In 1888, Britain started manufacturing a very similar mixture in Lydd, Kent, under the name Lyddite. Japan followed with an "improved" formula known as shimose powder. 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 in Austria-Hungary. By 1894 Russia was manufacturing artillery shells filled with picric acid. Ammonium picrate (known as Dunnite or explosive D) was used by the United States beginning in 1906. However, shells filled with picric acid become highly unstable if the compound reacts with metal shell or fuze casings to form metal picrates which are more sensitive than the parent phenol. The sensitivity of picric acid was demonstrated in the Halifax Explosion. Picric acid was used in the Battle of Omdurman,[7] Second Boer War,[8] the Russo-Japanese War,[9] and World War I.[10] Germany began filling artillery shells with TNT in 1902. Toluene was less readily available than phenol, and TNT is less powerful than picric acid, but improved safety of munitions manufacturing and storage caused replacement of picric acid by TNT for most military purposes between the World Wars.[7]

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, i.e., aspirin, to keep it from the Allies. See Great Phenol Plot. 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 support the war effort.[11] Both Monsanto[12] and Dow Chemical[13] undertook manufacture of synthetic phenol in 1915. Dow was the leading producer. 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.”[14]

Thomas Edison needed phenol to manufacture phonograph records. Edison responded by undertaking production of phenol at his Silver Lake, NJ, facility using processes developed by his chemists.[15] He built two plants with a capacity of six tons of phenol per day. Production began the first week of September, one month after hostilities began in Europe. He built two plants to produce raw material benzene at Johnstown, PA and Bessemer, AL, replacing supplies previously from Germany. Edison also manufactured aniline dyes, which previously had been supplied by the German dye trust. Other wartime products include xylene, p-phenylenediamine, shellac, and pyrax. Wartime shortages made these ventures profitable. In 1915, his production capacity was fully committed by midyear.

Other Languages
العربية: حمض البيكريك
azərbaycanca: Trinitrofenol
تۆرکجه: پیکریک اسید
беларуская: Трынітрафенол
dansk: Pikrinsyre
Deutsch: Pikrinsäure
Ελληνικά: Πικρικό οξύ
español: Ácido pícrico
euskara: Azido pikriko
français: Acide picrique
한국어: 피크린산
íslenska: Pikriksýra
italiano: Acido picrico
kaszëbsczi: Melinit
қазақша: Мелинит
latviešu: Pikrīnskābe
lietuvių: TNP
magyar: Pikrinsav
Bahasa Melayu: Asid pikrik
Nederlands: Picrinezuur
日本語: ピクリン酸
norsk: Pikrinsyre
oʻzbekcha/ўзбекча: Trinitrofenol
português: Ácido pícrico
română: Acid picric
slovenčina: 2,4,6-trinitrofenol
slovenščina: Pikrinska kislina
српски / srpski: Pikrinska kiselina
srpskohrvatski / српскохрватски: Pikrinska kiselina
svenska: Pikrinsyra
Türkçe: Pikrik asit
українська: Пікринова кислота
Tiếng Việt: Axit picric
中文: 苦味酸