Scottis­h police officer all suited up to handle mustard gas

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Definition and Chemistry of Mustard Gas

Before we learn how mustard gas works, it's important to understand what a gas is in terms of chemical warfare. Just the word "gas" may lead people to think that the substance is a vapor. That's not entirely true. Gases in warfare can be any chemical substance, including gases, solids and liquids, and generally fall into one of three medical groups.

  1. Lethal gases can lead to disablement or death.
  2. Harassing agents don't cause casualties but disrupt enemy soldiers.
  3. Accidental gases includes gases soldiers may encounter during war that are not directly related to a chemical weapon, such as excessive gases from gunpowder during a firefight.

Mustard gas or mustard agent is a poisonous gas that falls in the first group, along with even more lethal chemical agents such as chlorine gas and sarin. Tear gas, for example, is a non-poisonous gas that falls in the second category. Although tear gas is an effective weapon against advancing soldiers, it has no deadly effects. The same can't be said about mustard gas.

Mustard gas, also called sulfur mustard, gets its name from its sometimes yellow appearance and mustardlike smell. It's referred to as a blister agent or a vesicant, and comes in vapor, solid or liquid form. Other blister agents include nitrogen mustard, lewisite and­ phosgene oxime.

Blister agents are no fun. Once in contact with an unsuspecting victim, they damage skin and internal areas such as mucous membranes inside your nose and throat. Mustard gas is an alkylating agent, meaning its chemicals destroy DNA and cells and liquefy tissue. In essence, mustard gas kills tissue and membranes in the areas it touches. Alkylating agents also are often used in cancer drugs.

As you might have picked up, mustard gas is very dangerous, especially compared to tear gas. If you measured mustard gas on a scale of one to 10, with 10 being the scariest, mustard gas would come in around a seven. Compared to Zyklon-B, the gas pellets used in gas chambers during the Holocaust, mustard gas seems tame. But that doesn't mean it hasn't caused its fair share of fatalities. A little bit later on, we'll look at some of the devastation mustard gas brought on during warfare.

Mustard gas comprises four elements found on the periodic table: carbon, sulfur, chlorine and hydrogen. The sulfur and carbon lend to the gaseous appearance and smell in both solid and liquid states. The exact molecular formula is C4H8Cl2S.

In its crude state, mustard gas resembles used motor oil: heavy and sludgy. Because of a relatively high freezing point of 58 degrees Fahrenheit (14 degrees Celsius), mustard gas proved a less effective weapon in colder temperatures. It wouldn't spread throughout a large area, and it would fall to the ground before troops inhaled the deadly gas.

Mustard gas isn't something you find in nature. You won't discover it under a rock or buried in a mine shaft. The chemists who stumbled upon the compound quickly realized it could be deadly and even fatal if inhaled. Many credit Fredrick Guthrie as the first to synthesize mustard gas in 1860 , and Dow Chemical as the first company to produce it (during World War I) [source: Holland].

Next, we'll explore the origins of mustard gas in warfare and delve into the reasons behind the decision to use it as a weapon.­