Picric acid

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For the airport with the IATA airport code TNP, see Twentynine Palms Airport.

Picric acid

General
Systematic name	2,4,6-trinitrophenol
Other names	Carbazotic Acid phenol trinitrate picronitric acid trinitrophenol 2,4,6-trinitro-1-phenol 2-hydroxy-1,3,5-trinitrobenzene
Molecular formula	(NO₂)₃C₆H₂OH
SMILES	Oc1c(N(=O)=O)cc (N(=O)=O)cc1N(=O)=O
Molar mass	229.1056 g/mol
Appearance	Colorless-yellow solid.
CAS number	[88-89-1]
Properties
Density and phase	1.763 g/cm³, solid.
Solubility in water	1.40 g/100 ml (?°C)
Melting point	122.5°C (395.65 K)
Boiling point	Explodes > 300°C (573.15 K)
Acidity (pK_a)	0.38
Structure
Molecular shape	Planar.
Crystal structure	?
Dipole moment	? D
Hazards
MSDS	External MSDS
Main hazards	Explosive, flammable, irritant, toxic.
NFPA 704	4 3 4 OX
Flash point	150°C
R/S statement	R: R1, R10, R36, R37, R38. S: S28, S35, S37, S45.
RTECS number	TJ7875000
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Related Phenols	?
Related compounds	?
Except where noted otherwise, data are given for materials in their standard state (at 25°C, 100 kPa) Infobox disclaimer and references

Picric acid is the common term for the chemical compound 2,4,6-trinitrophenol, also known as TNP; the material is a yellow crystalline solid. Like other highly nitrated compounds (e.g. trinitrotoluene), picric acid is an explosive.

Modern safety precautions recommend storing picric acid wet. When picric acid is dry, it is relatively sensitive to shock and friction, so laboratories that use it store it in bottles under a layer of water, rendering it safe. Glass or plastic bottles are required, as picric acid can form metal picrate salts that are even more sensitive and hazardous than the acid.

1 Properties
2 History
3 Uses
4 Other
5 See also
6 External links
7 References

[edit] Properties

Velocity of detonation: 7,350 m/s at density 1.70
Autoignition temperature: Explodes over 300 °C

Picric acid can be made from phenol, benzene (in the Wolfenstein-Boters reaction), or even acetylsalicylic acid (aspirin).

[edit] History

Picric acid was 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. Before then, chemists assumed that only the salts of picric acid were explosive, not the acid itself. In 1873 Hermann Sprengel proved it could be detonated and by 1894 the Russians had worked out a method of manufacture for artillery shells. Soon after, every military power used picric acid as their primary high explosive material. However, shells filled with picric acid become highly unstable as the compound reacts with the bomb casing to form extremely sensitive metal picrates, and the 20th century saw picric acid largely replaced by TNT. Picric acid is also used in the analytical chemistry of metals, ores, and minerals.

Picric acid was one of the main components in the Halifax Explosion.

In 1885, based on research of Hermann Sprengel, French chemist Eugene Turpin patented the use of pressed and cast picric acid in blasting charges and artillery shells. In 1887 the French government adopted it under the name melinite, with addition of 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.

[edit] Uses

By far the largest use has been in munitions and explosives; it was known in World War I as Lyddite (from Lydd, Kent, where the British undertook work to develop it as a shell filling) or Melinite.

The principal laboratory use of picric acid is in microscopy, where it is used as a reagent for staining samples, e.g. Gram staining.

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 is not acidic enough to cause chemical burns, and reacts with proteins in the skin to give a dark brown color that may last as long as a month.

[edit] Other

Picric acid is well known as another easy 'homemade explosive,' since its synthesis requires chemicals that can be bought at a convenience store or pharmacy. Many people have injured or killed themselves during the synthesis of picric acid. During its synthesis the highly toxic nitrogen dioxide gas can be produced.