Picric acid
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| Names | |||
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Preferred IUPAC name
2,4,6-Trinitrophenol
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| Other names
Picric acid
Carbazotic acid Phenol trinitrate Picronitric acid Trinitrophenol 2,4,6-Trinitro-1-phenol 2-Hydroxy-1,3,5-trinitrobenzene TNP Melinite |
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| Identifiers | |||
88-89-1 
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| 3D model (Jmol) | Interactive image | ||
| ChEBI |
CHEBI:46149
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| ChEMBL |
ChEMBL108541
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| ChemSpider |
6688
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| DrugBank |
DB03651
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| ECHA InfoCard | 100.001.696 | ||
| PubChem | 6954 | ||
| RTECS number | TJ7875000 | ||
| UNII |
A49OS0F91S
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| Properties | |||
| C6H3N3O7 | |||
| Molar mass | 229.10 g·mol−1 | ||
| Appearance | Colorless to yellow solid | ||
| Density | 1.763 g·cm−3, solid | ||
| Melting point | 122.5 °C (252.5 °F; 395.6 K) | ||
| Boiling point | > 300 °C (572 °F; 573 K) Explodes | ||
| 12.7 g·L−1 | |||
| Vapor pressure | 1 mmHg (195 °C) | ||
| Acidity (pKa) | 0.38 | ||
| -84.34·10−6 cm3/mol | |||
| Hazards | |||
| Main hazards | explosive | ||
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EU classification (DSD)
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 T  E  F+
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| R-phrases | R1 R4 R11 R23 R24 R25 | ||
| S-phrases | S28 S35 S37 S45 | ||
| NFPA 704 | |||
| Flash point | 150 °C; 302 °F; 423 K | ||
| Lethal dose or concentration (LD, LC): | |||
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LDLo (lowest published)
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100 mg/kg (guinea pig, oral) 250 mg/kg (cat, oral) 120 mg/kg (rabbit, oral) |
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| US health exposure limits (NIOSH): | |||
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PEL (Permissible)
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TWA 0.1 mg/m3 [skin] | ||
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REL (Recommended)
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TWA 0.1 mg/m3 ST 0.3 mg/m3 [skin] | ||
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IDLH (Immediate danger)
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75 mg/m3 | ||
| Explosive data | |||
| Detonation velocity | 7,350 m·s−1 at ρ 1.70 | ||
| RE factor | 1.20 | ||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is  ?) |
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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, which was once 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. 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. 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 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 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,Second Boer War, the Russo-Japanese War, and World War I. 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.
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