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Title: Chloropicrin  
Author: World Heritage Encyclopedia
Language: English
Subject: Chemical warfare, Nerve agent, Nettle agent, Novichok agent, Pulmonary agents
Collection: Fumigants, Lachrymatory Agents, Nitroalkanes, Nitromethanes, Pulmonary Agents, Vomiting Agents, World War I Chemical Weapons
Publisher: World Heritage Encyclopedia


IUPAC name
Other names
PS, Nitrochloroform, Trichloronitromethane, Nitrotrichloromethane
ChemSpider  Y
Jmol-3D images Image
Molar mass 164.375 g/mol
Appearance colorless liquid
Odor irritating[1]
Density 1.692 g/ml[2]
Melting point −69 °C (−92 °F; 204 K)
Boiling point 112 °C (234 °F; 385 K) (decomposes)
Vapor pressure 18 mmHg (20°C) [1]
Main hazards Extremely toxic and irritating to skin, eyes, and lungs.
GHS pictograms The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word Danger
Very Toxic T+
R-phrases R50/53
S-phrases S36/37, S38, S45
NFPA 704
Lethal dose or concentration (LD, LC):
9.7 ppm (mouse, 4 hr)
117 ppm (rat, 20 min)
14.4 ppm (rat, 4 hr)[3]
293 ppm (human, 10 min)
340 ppm (mouse, 1 min)
117 ppm (cat, 20 min)[3]
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 0.1 ppm (0.7 mg/m3)[1]
REL (Recommended)
TWA 0.1 ppm (0.7 mg/m3)[1]
2 ppm[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 Y  (: Y/N?)

Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide.[4] Its chemical structural formula is Cl3CNO2.


  • Discovery 1
  • Properties 2
  • Use 3
  • Safety 4
    • Agriculture 4.1
      • California 4.1.1
    • High Concentrations 4.2
  • Preparation 5
  • References 6


Chloropicrin was discovered in 1848 by Scottish chemist John Stenhouse. He prepared it by the reaction of a chlorinating agent with picric acid:

HOC6H2(NO2)3 + 11 NaOCl → 3 Cl3CNO2 + 3 Na2CO3 + 3 NaOH + 2 NaCl

Because of the precursor used, Stenhouse named the compound chloropicrin, although the two compounds are structurally dissimilar.


Chloropicrin’s chemical formula is CCl3NO2 and its molecular weight is 164.38 grams/mole.[5] Pure chloropicrin is a colorless liquid, with a boiling point of 112 °C.[5] Chloropicrin is sparingly soluble in water with solubility of 2000 mg/L at 25 °C.[5] It is volatile, with a vapor pressure of 23.2 millimeters of mercury (mm Hg) at 25 °C; the corresponding Henry’s Law Constant is 0.00251 atmosphere-cubic meter per mole.[5] The octanol-water partition coefficient (Kow) of chloropicrin is estimated to be 269.[5] Its soil adsorption coefficient (Koc; normalized to soil organic matter content) is 25 cm3/g.[5]


Chloropicrin was manufactured for use as poison gas in World War I.[6] In agriculture, chloropicrin is injected into soil prior to planting a crop in order to fumigate soil. Chloropicrin affects a broad spectrum of fungi, microbes, insects.[7][8] It is commonly used as a stand alone treatment or in combination / co-formulation with methyl bromide and 1,3-Dichloropropene.[8][9]


At the national level, chloropicrin is regulated by the United States Environmental Protection Agency as a restricted use pesticide.[7][10] The EPA has approved chloropicrin as safe for use by farmers nationwide. The distribution and use of chloropicrin is available only to licensed professionals and specially certified growers who are trained in its proper and safe use.[7][10] In the US, occupational exposure limits have been set at 0.1 ppm over an eight-hour time-weighted average.[11]


In 2008 the US EPA re-approved chloropicrin as safe for use in agricultural settings, stating that treatments "can provide benefits to both food consumers and growers. For consumers, it means more fresh fruits and vegetables can be cheaply produced domestically year-round because several severe pest problems can be efficiently controlled."[12][13][14] To ensure chloropicrin is used safely, the EPA requires a strict set of protections for handlers, workers, and persons living and working in and around farmland during treatments.[7][13] EPA protections were increased in both 2011 and 2012, reducing fumigant exposures and significantly improving safety.[15] Protections include the training of certified applicators supervising pesticide application, the use of buffer zones, posting before and during pesticide application, fumigant management plans, and compliance assistance and assurance measures.[14][16]


In California experience with acute effects of chloropicrin when used a soil fumigant for strawberries and other crops led to the release of regulations in January 2015 creating buffer zones and other precautions to minimize exposure of farm workers, neighbors, and passersby.[17][18]

High Concentrations

Unlike its use in agriculture, in unregulated settings chloropicrin can be harmful to humans. Chloropicrin can be absorbed systemically through inhalation, ingestion, and the skin. At high concentrations it is severely irritating to the lungs, eyes, and skin.[19] In World War I German forces used concentrated chloropicrin against Allied forces as a tear gas. While not as lethal as other chemical weapons, it caused vomiting and forced Allied soldiers to remove their masks to vomit, exposing them to other, more toxic chemical gases used as weapons during the war.[9]


Chloropicrin is manufactured by the reaction of nitromethane with sodium hypochlorite:[20]

H3CNO2 + 3 NaOCl → Cl3CNO2 + 3 NaOH


  1. ^ a b c d e f "NIOSH Pocket Guide to Chemical Hazards #0132".  
  2. ^
  3. ^ a b "Chloropicrin". Immediately Dangerous to Life and Health.  
  4. ^ "RED Fact Sheet: Chloropicrin" (PDF). US Environmental Protection Agency. 10 July 2008. p. 2. Retrieved 20 September 2013. 
  5. ^ a b c d e f "Executive Summary - Evaluation of Chloropicrin As A Toxic Air Contaminant" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. February 2010. p. iv. Retrieved 20 September 2013. 
  6. ^ Ayres, Leonard P. (1919). The War with Germany (Second ed.). Washington, DC: United States Government Printing Office. p. 80. 
  7. ^ a b c d "Chloropicrin - Background". Retrieved 20 September 2013. 
  8. ^ a b
  9. ^ a b Amos Alfred Fries; Clarence Jay West (1921). Chemical warfare. McGraw-Hill book company, inc. p. 144. 
  10. ^ a b "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 1. Retrieved 20 September 2013. 
  11. ^ "NIOSH Pocket Guide to Chemical Hazards". Centers for Disease Control and Prevention. Retrieved 7 November 2013. 
  12. ^ "Amended Reregistration Eligibility Decision (RED) for Chloropicrin" (PDF). United States Environmental Protection Agency. May 2009. Retrieved 20 September 2013. 
  13. ^ a b "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 2. Retrieved 20 September 2013. 
  14. ^ a b "Environmental Protection Agency (EPA) Re-Registers Chloropicrin As Safe For Use Nationwide". Retrieved 22 October 2013. 
  15. ^ "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 2. Retrieved 20 September 2013. The Amended RED incorporated final new safety measures to increase protections for agricultural workers and bystanders. These measures establish a baseline for safe use of the soil fumigants throughout the United States, reducing fumigant exposures and significantly improving safety. 
  16. ^ "Chloropicrin - Frequently Asked Questions". Retrieved 21 October 2013. 
  17. ^ "Control Measures for Chloropicrin" (PDF). California Department of Pesticide Regulation. January 6, 2015. Retrieved January 15, 2015. added controls for chloropicrin when it is used as a soil fumigant. The controls are intended to reduce risk from acute (short-term) exposures that might occur near fields fumigated with products containing chloropicrin. 
  18. ^ "Chloropicrin Mitigation Proposal" (PDF). Department of Pesticide Regulation - California Environmental Protection Agency. 15 May 2013. p. 2. Retrieved 20 September 2013. The new measures appearing on soil fumigant Phase 2 labels include buffer zones and posting, emergency preparedness and response measures, training for certified applicators supervising applications, Fumigant Management Plans, and notice to State Lead Agencies who wish to be informed of applications in their states. 
  19. ^ Chloropicrin (PS): Lung Damaging Agent. National Institute for Occupational Safety and Health. Emergency Response Safety and Health Database, August 22, 2008. Retrieved December 23, 2008.
  20. ^ Sheldon B. Markofsky "Nitro Compounds, Aliphatic" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005.
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