CW Agent Factsheet - Soman

Alternative codes and names

Colourless liquid, which gives off an odour of rotting fruit when vaporizing. The vapour is colourless. The lethal dose for soman through inhalation is about half that of sarin. It is also a far more persistent agent than sarin so that it can easily remain in a particular area for a day or longer, depending on the atmospheric conditions.

Nerve agents in general attack the nervous system of the human body.When a nerve receives a stimulus acetylcholine is released in order to carry the impulse to muscles and organs. Once the impulse has passed the enzyme cholinesterase acts to prevent the accumulation of acetylcholine after its release in the nervous system. Nerve agents inhibit the functioning of cholinesterase, as a consequence of which the acetylcholine continues to act so that nervous impulses keep on being transmitted. The first symptoms a victim will experience following exposure to nerve agents are a runny nose, tightness in the chest and constriction of the pupils (miosis). The victim will then encounter breathing difficulties, drooling from the mouth and nausea. Because he loses control over his bodily functions, he will involuntary vomit, defecate and urinate. This phase is followed by twitching and jerking. Ultimately the victim will become comatose and suffocate as a consequence of convulsive spasms.

Soman is extremely toxic by absorption through the skin and death will follow about 15 minutes after a lethal dose has been absorbed. In case of inhalation or absorption of a lethal dose through the eyes, death will occur between 1 and 10 minutes. Soman is readily absorbed into the bloodstream and reacts immediately with neural tissue, particularly in the brain, which explains its greater lethality. Inhibited acetylcholinesterase cannot be reactivated, so that some forms of medical treatment against nerve agents, such as oxime-based drugs to give the body time to destroy and excrete the toxic substances, are useless against soman.

Key precursors: methylphosphonyl difluoride; methylphosphonyldichloride

Precursors: Dimethyl methylphosphonate

Other chemicals: Trimethylphosphite; phosphorus trichloride

Although the third nerve agent developed in Germany, soman received the Allied coding GD. No chemical agent was ever coded GC, as it used to be the medical reference for the disease gonorrhea. While continuing the research after the discovery of sarin, the German chemists first came across a more toxic substance, called T-210, which was apparently not further developed, before discovering soman in 1944. The origin of the name is uncertain and may have been derived from Greek ('sleep') or Latin ('bludgeon').

After World War II, soman was incorporated into the Soviet arsenals. A thickened variant was developed for use in 250kg chemical spray tanks. The thickened soman is a yellowish-brown, highly viscous liquid with a slight aromatic odour. During the 1980s, many Western sources referred to this agent as VR-55, but more recent literature identifies VR-55 as an isomer of VX.