Firstly, and before I forget, a very Happy New Year to all of my readers! I hope you had a good one wherever in the world you are.

I have been meaning to write this for a while but other blog posts seem to get in the way! The post was developed after I read a news article about CS gas being accidently sprayed at London City Airport towards the end of October last year (

I should point out that CS gas is also commonly called tear gas in the media.

I also (incorrectly) thought that CS gas was Carbon Sulfide (ie CS2) – well, it works on paper doesn’t it? (Be honest, I expect you did as well!) but as you can probably imagine, CS gas is not Carbon Sulfide. It is, in fact, wait for it…..2-Chlorophenyl)methylidene]propanedinitrile. It is favoured as it is a non lethal leathal chemical agent that irritates the mucous membranes of the eyes, nose, mouth and lungs. People exposed to it cannot keep their eyes open and experience coughing, disorientation and difficulty breathing.

Public Domain,

In very simple terms, the irritation caused by CS gas is due to a chemical reaction with a sulfur group in enzymes1.

This made me go on and think about the role of chemistry in war fare and I did a little more digging. Chemistry has also been used to make leathal weapons. In the 19th century, Humphry Davey was invited by the British government to invent a Chlorine based chemical weapon (Davey was an expert on Chlorine).

To his credit he saw it as highly immoral and would have nothing to do with it. Only in 1914, with the onset of the first World War did the German Chemist Fritz Haber develop cholrine gas as a weapon.

World War 1 is often thought of as being a ‘Chemist’s War’, a race between the devisers of offensive chemicals and devisers of protective

measures such as gas masks.

By the time World War 2 came along the extremely deadly organophosphrous nerve gases had been invented but mercifully they were not deployed.

Nature invented chemical weapons long before humans thought about invented them. Mammalian bodies are always on guard against bacterial invaders. The human body produces the deadly .OH (hydroxyl) radical through the following reaction:

H2O2 + O2–> OH+ O2 + .OH

This hydroxyl radical will attack any bacterial invader by chemically reacting with it.

There are plenty more examples of chemistry in lethal and non lethal chemical weapons. Do you have any favourtites? And how do they work?

1 Adapted from