Soman is usually ignored by the media in favor of other nerve agents such as Sarin or VX. Despites such obscurity, Soman remains an important component of chemical warfare. Also known as GD, Soman is another of the G-class nerve agents along with Sarin (GA) and Tabun (GB).
Structure and Form:
Like all other nerve agents, Soman is a fluorinated organophosphorus ester. Mostly commonly referred to as methylphosphonofluoridic acid 1,2,2-trimethylpropyl ester, its chemical formula is C7H16FO2P. The chemical structure is very similar to that of Sarin, C4H10FO2P. Consequently the two agents appear quite similar; normally the nerve agent exists a colorless liquid which vaporizes to a colorless gas.
It exists in mainly two forms: the standard liquid form and a military-grade thickened form (TGD). The commonly accepted means for thickening Soman is the addition of styrene-butyl acrylate copolymer resulting in a highly-viscous yellow-brown solution.
All versions of Soman give off a slight aromatic scent. Military-grade Soman smells sweet and fruity while the cruder industrial-grade Soman bears a camphor scent.
Mechanism:
Soman is a cholinesterase inhibitor acting very similar to Tabun. Acetylcholine (ACh) is generated by nerves to conduct electrical signals and transmit impulses throughout the central nervous system. When the acetylcholine is no longer useful, the enzyme cholinesterase (ChE) removes it from the system. Soman prevents the cholinesterase from breaking down the acetylcholine and terminating the stimulation.
As a result, systematic symptoms of neurotoxicity can be seen in the victims. At small doses, these symptoms includes uncontrollable body tremors, nausea, and weakness. However, due to the potency of Soman, all doses are generally high and paralysis and death occur. Since the victim loses all control of his body, he may vomit, defecate, and, urinate while twitching before he finally suffocates to death. For this reason, chemical weapons such as Soman induce fear and panic in the general public and work well as a terror weapon.
History:
Soman was first discovered in 1944 by a German scientist, Richard Kuhn, while researching Tabun and Sarin. The discovery came too late to be of any practical use to the Nazi Regime. To prevent capture, all the details of the research were hidden in a mineshaft east of Berlin. When the Soviets occupied East Berlin, they found the documents and began stockpiling the substance.
Application:
Nerve agents are used to kill organisms with complex nervous systems, mainly humans. (The initial discovery of Tabun, the first nerve agent, came from pesticide research.)
There are two ways to transport and deliver nerve agents: unitary and binary munitions. Unitary weapon systems store the actual Soman substance while binary weapon systems store components of Soman that are mixed upon detonation. Generally, the United States' military-industrial complex has no difficulty with the technical expertise required or cost of binary munitions; however, most underdeveloped nations (i.e. all the countries not in G7) usually prefer the unitary method. Quite intuitively, the binary method is much safer and more reliable. Unitary munitions also have a shorter shelf life and are generally undesirable.
The actual weapon system can be used in many ways, limited only by human creativity/depravity. Conventional artillery, ballistic missiles, cruise missiles, bombs, mortars, landmines, and multiple launch rocket systems are generally the accepted means of delivery. However, Soman is very deadly and wind conditions will affect greatly the distribution in most cases. For small amounts, such as the amount in a landmine, the effects of wind are negligible. Otherwise, a change in wind direction may bring the plume of invisible gas towards the user.
Most nations with high budgets use cruise missiles and laser guided bombs but a SCUD will work just fine in most cases.
The thickened version can also be used from a chemical spray tank.
Effectiveness:
Soman will kill if inhaled or absorbed through the skin. Death occurs quickly, usually between 1 and 10 minutes. Compared to the other G-class nerve agents Soman is much more potent since it is readily absorbed into the bloodstream and carried to the brain. Soman has a human LCt50 of 70 mg-min/m3. In other words, 50% of those subjected to a concentration of 70 mg/m3 for a minute will end up dead.
Treatment:
After a Soman attack, the enzyme cholinesterase no longer works to control the levels of acetylcholine. Consequently the two accepted forms of treatment for nerve agents involve either reactivating the enzyme cholinesterase or inhibiting acetylcholine. Oxime-based drugs such as HI-6 reactivate cholinesterase. Atropine acts to inhibit acetylcholine. Current United States military guidelines indicate the administration of HI-6 with atropine. However, this treatment regime is ineffective against Soman.
Protection:
The best and only reliable protection is to avoid contact. Failing that, NATO Standard 40mm filters on a sealed gas mask will work rather well. Israeli and Russian surplus units are generally easily acquired if so desired.
Decontamination:
Soman is easily hydrolyzed in basic solutions. Hypochlorite anion (OCl-) is usually used to catalyze the reaction. In a solution of pH 11, the half-life of Soman is about a minute.
Physical Properties:
Formula Weight: 182.19 g
Melting Point: -80 to -42°C
Boiling Point: 190 to 198°C
Vapor Pressure at 20°C: 0.92 mm Hg
Density at 20°C: 1.01 g/cm3
Volatility at 0°C: 531 mg/m3
Volatility at 25°C: 3900 mg/m3
Volatility at 30°C: 5570 mg/m3
Specific Gravity at 25°C: 1.0252
Aqueous Solubility at 0°C: 34 g/L
log Kow: 1.78
log Kbenzene-water: 1.61
Sources:
http://www.bt.cdc.gov/Agent/Nerve/Soman/Soman.asp
http://www.bt.cdc.gov/agent/Nerve/Soman/ctc0004.asp
http://projects.sipri.se/cbw/cbw-agents/Soman.html
http://www.mitretek.org/home.nsf/homelandsecurity/HistoryNerveGases
http://www.wikipedia.org/wiki/Soman
http://www.geocities.com/CapeCanaveral/Lab/7050/properties.html
http://www.mitretek.org/home.nsf/homelandsecurity/Soman
http://www.geocities.com/CapeCanaveral/Lab/7050/usuage.html