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Destroying chemical weapons

Brigitte Osterath / ew
December 14, 2013

Although chemical warfare agents such as sarin and VX are highly lethal, they are relatively easy to neutralize. One of the best methods of doing it is with water, in a simple but efficient process known as hydrolysis.

Sign with the name sarin
Image: Philipp Guelland/AFP/Getty Images

What will happen with Syria's chemical weapons? According to a plan laid out by the Organization for the Prohibition of Chemical Weapons (OPCW), the world's chemical watchdog, the aim is to have them destroyed by mid-2014. And the US has offered assistance: According to OPCW, the chemical stockpile is to be destroyed onboard a US navy ship in international waters.

A simple way of neutralizing chemical warfare agents is combustion. Nerve agents such as sarin and VX are liquids and, like most chemical compounds in their category, they are combustible. Heat breaks down the molecules into smaller, non-toxic particles.

But there is also another method, which is more sophisticated. The toxic substances can be neutralized through a chemical reaction called hydrolysis - when chemical compounds decompose on contact with water.

Highly reactive - and vulnerable

Both sarin and VX have one major weakness: a molecular structure that makes them react easily with other substances. While this property makes them extremely poisonous, it also allows them to be easily neutralized. Water molecules can easily attach themselves to the poisonous molecules, changing their structure and making them non-toxic.

OPCW headquarters in The Hague
An OPCW plan calls for destroying the chemical weapons at seaImage: Evert-Jan Daniels/AFP/Getty Images

Nevertheless, the resulting substances still require a special method of disposal based on international regulations. This is because the hydrolysis reaction is theoretically reversible, meaning that the neutralized substance can in some cases start producing toxic vapors again. However, using large amounts of water makes this scenario extremely unlikely.

Even normal water from the faucet has the power to neutralize the poisons. However, it is a slow process: sarin's toxicity, for example, would only decrease by half over a period of three days. A much faster method is using water with a high pH value - in other words, with a high alkaline level, making it capable of neutralizing acidic substances such as sarin. Water with a pH of 9 can break down sarin by 50 percent in less than one hour.

A tailor-made destruction plant

The US military has already developed an apparatus for neutralizing chemical weapons in bulk: the Field Deployable Hydrolysis System (FHDS). According to an official statement, this mobile neutralizer has a destruction efficiency of 99.9 percent and can neutralize between five and 25 metric tons of chemicals per day.

Chemical weapons inspectors in Syria
Chemical weapons inspectors in Syria located tons of nerve agentsImage: picture alliance/AP Photo

The key component of the FHDS is an 8,328-liter (2,200-gallon) titanium reactor, in which the toxic agents are mixed with water and other chemicals. A built-in heating system speeds up the neutralization process. The contents are only removed once the poisonous substances have broken down completely. To prevent the escape of any lethal vapors, the entire apparatus is housed inside an expandable, gas-tight structure.

The FHDS can be set up anywhere within 10 days. This includes ships, such as the US Navy vessel MV Cape Ray, which is set to destroy Syria's chemical weapons at sea.