Picric acid



"TNP" redirects here. For the airport with the IATA airport code TNP, see Twentynine Palms Airport.
Picric acid
IUPAC 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; TNP
Identifiers
CAS number 88-89-1
RTECS number TJ7875000
SMILES O=[N+]([O-])c1cc(cc([N+]([O-])=O)c1O)[N+]([O-])=O
Properties
Molecular formula C6H3N3O7
Molar mass 229.10 g/mol
Appearance Colorless to yellow solid
Density 1.763 g/cm³, solid
Melting point

122.5 °C

Boiling point

> 300 °C (Explodes)

Solubility in water 1.40 g/100 mL
Acidity (pKa) 0.38
Hazards
NFPA 704
4
3
4
 
R-phrases R1 R10 R36 R37 R38
S-phrases S45
Explosive data
Explosive velocity 7,350 m/s at ρ 1.70
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 TNT, picric acid is an explosive. Its name comes from Greek πικρος - bitter, reflecting the bitter taste of picric acid.

History

Picric acid was probably first mentioned in the 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 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

Picric acid can be made by nitration of aspirin).

Uses

By far the largest use has been in munitions and explosives, as discussed above.

In microscopy, picric is used as 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. 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 salts that are even more sensitive and hazardous than the acid. In a 2007 incident, pharmacy employees in Columbus, Wisconsin found a World War I-era bottle containing two ounces of the liquid, which required a visit from the bomb squad for safe disposal.[1] Improper lab handling can also turn picric acid into a dangerous chemical as illustrated in another 2007 incident, where a bomb squad dispatched to a forensic crime laboratory in Hayward, California caused numerous civilians to be evacuated while the chemical was intentionally detonated.[2]

References

  1. ^ "Old Sample of Acid Detonated in Wis." (reprint), Associated Press, 16 Apr 2007. 
  2. ^ "Bomb Squad Detonates Acid At Hayward Lab", KTVU.com, 22 Aug 07. 
  • Cooper, Paul W., Explosives Engineering, New York: Wiley-VCH, 1996. ISBN 0-471-18636-8
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Picric_acid". A list of authors is available in Wikipedia.