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Sarin

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Sarin
Discovery
Discovered by Gerhard Schrader
Ambrose
Rüdiger
van der Linde
Discovered in 1938
Chemical Characteristics
Chemical Name O-Isopropyl Methylphosphonofluoridate
Chemical Family Fluorinated organophosphorus compound
Chemical Formula CH3P(O)(F)OCH(CH3)2
NFPA Rating
  • Health – 4
  • Flammability – 1
  • Reactivity – 1 </small>
Airborne Exposure Limit 0.0001 mg/m3
Boiling Point 158 °C
Freezing/Melting Point -56 °C
Vapor Pressure 2.9 at 25 °C
Vapor Density (Air=1) 4.86
Liquid Density 1.0887 at 25 °C/1.102 at 20 °C
Solubility in Water Complete
Specific Gravity 1.0887 at 25 °C
Appearance and Color Colorless liquid. Odorless in pure form.
Precursors
Key precursors methylphosphonyl difluoride
methylphosphonyl dichloride
diisopropyl methylphosphonochloridate
Precursors Dimethyl methylphosphonate
isopropyl methylphosphonate
Other chemicals Trimethylphosphite
phosphorus trichloride
triisopropyl phosphite

Sarin or GB (O-Isopropyl methylphosphonofluoridate) is an extremely toxic substance that is one of the world's most dangerous weapons of war. As a chemical weapon, it is classified as a weapon of mass destruction by the United Nations according to UN Resolution 687, and its production and stockpiling was outlawed by the Chemical Weapons Convention of 1993.

Table of contents

Chemical Characteristics

Sarin is similar in structure and biological activity to some commonly used insecticides, such as Malathion, and is similar in biological activity to carbamates used as insecticides such as Sevin, and medicines such as Mestinon, Neostigmine, and Antilirium.

At room temperature, sarin is a colourless, odorless liquid. Its relatively high vapor pressure means that it evaporates quickly (about 36 times as quickly as tabun, another common chemical nerve agent). Its vapor is also colorless and odorless. It can be made more persistent through the addition of certain oils or petroleum products.

Sarin can be used as a binary chemical weapon; its two precursors are methylphosphonyl difluoride and a mixture of isopropyl alcohol and isopropyl amine. The isopropyl amine binds the hydrogen fluoride generated during the chemical reaction.

Shelf Life

Sarin has a relatively short shelf life, and will degrade after a period of several months to several weeks. The shelf life may be greatly shortened by impurities in precursor materials. According to the CIA [1], in 1989 the Iraqis destroyed 40 or more tons of sarin that had decomposed, and that some Iraqi sarin had a shelf life of only a few weeks owing mostly to impure precursors.

Efforts to Lengthen Shelf Life

According to the CIA, nations such as Iraq have tried to overcome the problem of sarin's short self life in two ways:

  • The shelf life of unitary (i.e., pure) sarin may be lengthened by increasing the purity of the precursor and intermediate chemicals and refining the production process.
  • Developing binary chemical weapons, where the two precursor chemicals are stored separately in the same shell, and mixed to form the agent immediate before or when the shell is in flight. This approach has the dual benefit of making the issue of shelf life irrelevant and greatly increasing the safety of sarin munitions

Biological Effects

Like other nerve agents, sarin attacks the nervous system of the human body.

When a functioning motor nerve is stimulated it releases the neurotransmitter acetylcholine to transmit the impulse to a muscle or organ. Once the impulse has been sent, the enzyme acetylcholinesterase breaks down the acetylcholine in order to allow the muscle or organ to relax.

Sarin is an extremely potent organophosphate compound that disrupts the nervous system by inhibiting the cholinesterase enzyme by forming a covalent bond with the site of the enzyme where acetylcholine normally undergoes hydrolysis. This allows acetylcholine to build up and continue to act so that any nerve impulses is, in effect, continually transmitted.

Initial symptoms following exposure to sarin (and other nerve agents) are a runny nose, tightness in the chest and dilation of the pupils. Soon after, the victim has difficulty breathing and experiences nausea and drooling. As the victim continues to lose control of bodily functions, he vomits, defecates and urinates. This phase is followed by twitching and jerking. Ultimately, the victim becomes comatose and suffocates as a consequence of convulsive spasms.

Sarin is a highly volatile liquid. Inhalation and absorption through the skin pose a great threat. Even vapour concentrations immediately penetrate the skin. People who did not accumulate a lethal dose but did not receive immediate appropriate medical treatment may suffer permanent neurological damage.

Even at very low concentrations, sarin can be fatal. Death may follow in one minute after direct ingestion of about 0.01 milligram per kilogram of body weight if an antidote, typically atropine or other acetylcholine inhibitor, is not quickly administered.

It is estimated that sarin is more than 500 times as toxic as cyanide.

History

The following is the specific history of sarin, which is closely linked to the history of similar nerve agents also discovered in Germany during or soon after World War II. That broader history is detailed in Nerve Agent: History

Origin

This article forms part of the series
(A subset of Weapons of mass destruction)
Lethal agents
Blood agents
Cyanogen chloride
Hydrogen cyanide
Blister agents
Lewisite
Sulfur mustard gas (HD and THD, HT)
Nerve agents
G-Agents
GA (tabun), GB (sarin)
GD (soman), GF (cyclosarin)
V-Agents
VE, VG, VM, VX
Pulmonary agents
Chlorine
Phosgene
Diphosgene
Non-lethal agents
Incapacitating agents
BZ / Agent 15
KOLOKOL-1
Riot control agents
Pepper spray

Sarin was discovered in 1938 in Wuppertal-Elberfeld in the Ruhr valley of Germany by two German scientists while attempting to create stronger pesticides; it is the most toxic of the four G-agents made by Germany. The compound, which followed the discovery of the nerve agent tabun, was named in honor of its discoverers: Gerhard Schrader, Ambros, Rüdiger and Van der LINde.

Sarin in Nazi Germany During World War II

In mid-1939, the formula for the agent was passed to the Chemical Warfare section of the German Army Weapons Office, which ordered that it be brought into mass production for wartime use. A number of pilot plants were built, and a high-production facility was under construction (but was not finished) by the end of World War II. Estimates for total sarin production by Nazi Germany range from 500 kg to 10 tons.

Though sarin, tabun and soman were incorporated into artillery shells, Germany ultimately decided not to use nerve agents against Allied targets. German intelligence was unaware that the Allies had not developed similar compounds, and they were concerned that the Allies' ability to reach German targets would prove devastating in a chemical war.

Sarin after World War II

  • 1950's (early): NATO adopts sarin as a standard chemical warfare agent, and both Russia and the United States produce sarin for military purposes.
  • 1953: 20-year old Ronald Maddison, a Royal Air Force engineer from Consett, County Durham, died in human testing of sarin at the Porton Down chemical warfare testing facility in Wiltshire. Maddison had been told that he was participating in a test to "cure the common cold." After a 64-day inquest hearing, the jury ruled that Maddison had been unlawfully killed by the "application of a nerve agent in a non-therapeutic experiment."
  • 1956: Regular production of sarin ceased in the United States.
  • 1980-1988: Iraq and Iran both employed sarin in their 1980–88 war. During the 1990–91 Gulf War Iraq still had large stockpiles available.
  • 1988: Over the span of two days in March, the ethnic Kurd city of Halabja in northern Iraq (population 70,000) was bombarded with twenty chemical and cluster bombs, which included sarin. An estimated 5,000 people died. (see Halabja poison gas attack)
  • 1991: UN Resolution 687 establishes the term "weapon of mass destruction" and calls for the immediate destruction of chemical weapons in Iraq, and eventual destruction of all chemical weapons globally. [2]
  • 1993: The United Nations Chemical Weapons Convention is signed by 162 member countries, banning the production and stockpiling of many chemical agents, including sarin. It goes into effect on 29 April 1997, and calls for the complete destruction of all specified stockpiles of chemical agents by April 2007. [3]
  • 1998: In its June 15 issue Time Magazine ran a story entitled "Did The U.S. Drop Nerve Gas?". The story was broadcast June 7 on the CNN program NewsStand. The Time article alleged that U.S. Air Force A1E Skyraiders engaged in a covert operation called Operation Tailwind, in which they deliberately dropped CBU-15 Cluster Bomb Units containing submunitions that were filled with sarin on defected U.S. troops in Laos. The report caused a scandal, and The Pentagon launched a study which found that no gassing of U.S. soldiers took place. After an internal investigation, both CNN and Time magazine (both owned by the media conglomerate Time Warner) retracted the story and fired the reporters responsible for it. [4]
  • 2004: May 14 Iraqi insurgency fighters in Iraq detonate a 155 mm shell containing several litres of binary precursors for sarin. The shell was designed to mix the chemicals as it spun during flight. The detonated shell released only a small amount of sarin gas, either because the explosion failed to mix the binary agents properly, or the chemicals inside the shell had degraded significantly with age. Two United States soldiers were treated for exposure after displaying the early symptoms .[5]

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