The chemists' war

Reading Michael Freemantle's new book The Chemist's War 1914-1918 I am coming to appreciate that the First World War was won as much in the chemistry laboratory as on the battlefield. I have now reached the chapters dealing with the use of poison gases as weapons of mass destruction. Chemists were involved both in the design and production of toxic gases and in ways of protecting soldiers from their effects.

These are British gas helmets, an early form of gas mask consisting of a gas-permeable flannel hood treated with neutralising chemicals. It was worn over the head and tucked into the collar. The PH helmet, introduced in October 1915, was made of cloth treated with sodium phenolate, glycerin and hexamethylene tetramine, providing some protection against chlorine, phosgene and hydrocyanic acid. Around 14 million were made and it remained in service until the end of the war.

This contemporary photograph shows British machine gunners wearing PH helmets.