VX gas is one of the most dangerous chemicals created. It is used in chemical warfare. In the film "The Rock", it was that "green" liquid (though really a pale coloured oil) that the terrorists threatened San Francisco Bay area.

VX gas was developed in the Porton Down Chemical Weapons Research Centre, Wiltshire, England in 1952 and its devastating effects were tested. The British traded the technology of VX with the United States of America for information on thermonuclear weapons.

Its chemical formula is CH3CH20-P(O)(CH3)-SCH2CH2N(C3H7)2 and is normally in its liquid state despite its name. It has a low volatility; is odourless and is an excellent adhesive. A special form has been developed that is so adhesive that it is virtually impossible to remove from the surface that it is in contact with. This leads to strategic attacks on enemy bases or airfields so that the VX remains stuck to the area and has the potential to kill any one attempting to use the base or airfield.

The "V" of VX signifies it long persistence. So it is more dangerous and toxic than its cousins of the "G" variety like GA (Tabun) and GB (Sarin), which dissipate quickly and have only short-term effects. In the liquid form of VX, it is absorbed through the eyes or the skin of the victim. It takes an hour or two to take effect and its effects result in death. When aerosolized to give the gaseous form it more deadly than the liquid form and acts almost immediately on the victim. The effects are worst when it is inhaled and death is an end to the suffering.

The LD50 can be as little as 10mg for humans. It operates by cutting off the nervous system. It binds to the enzyme that transmits signals to the nerves and inhibits them. Therefore the nerves become isolated and uncontrollable. The antidote, atropine, is a toxin itself but it counteracts the effect of the VX by removing it from the enzyme. It is an anti-nerve agent so does the reverse of the VX, a nerve agent. It is normally injected into the arm or thigh but for gaseous attacks the atropine must go immediately into the heart. So full body protection and gas masks are essential to avoid exposure in a VX missile attack.

VX has not been used to its fullest potential yet because it is too dangerous to use for local attacks with wind that could blow the VX back onto the base. This factor has helped to keep VX from being used to cripple local nations. If these weapons were launched against a nation then there would be the possibility of a nuclear counterattack because VX is a weapon of mass destruction that spreads from impact point killing all in its path. This would be countered by another, which in a lot of cases, would be a nuclear bomb. The only known countries to possess VX are U.S. France and Russia. England after inventing it abandoned the thought for thermonuclear warfare.

There is no conclusive evidence, but it is believed that Saddam Hussein used VX against Iranian forces in the 1980-88 Iran-Iraq War, and then again in a 1988 chemical attack on Iraqi Kurds in the town of Halabja. That massacre reportedly killed 5,000 people and created serious health problems for thousands more.

Formal Chemical Name (IUPAC)
S-2-(diisopropylamino)ethyl O-ethyl methylphosphonothioate

References

http://old.krg.org/reference/halabja/index.asp

http://news.bbc.co.uk/onthisday/hi/dates/stories/march/16/newsid_4304000/4304853.stm