In 1913 German produced 135,000 of a global total of 163,000 tons of industrial dye. By one of the First World War’s ironies, German chemical works provided France with the dye for her soldiers red trousers.
Long before the word poilu came into use, France’s dashing soldiers in their Napoleonic uniforms of Red, White and Blue were known to the people as: les pantalons rouge.
In 1905 the French had thought long and hard about bringing the uniforms up to date, but the remark was made that the French Army was red trousers. Part of her later change to Horizon Blue was due to the fact that the enemy were no longer supplying the garance dye.
To manufacture these huge amounts of dye the Germans created thousands of tons of chlorine – every month – and about 650 tons of phosgene.
Inevitably there had been accidents amongst the workforce and German scientists were constantly searching for means to protect the labourers from these toxic gases.
As the wartime naval blockade by the Royal Navy took hold, Germany’s chemical industry was set to work on finding new ways of replacing natural materials.
Inevitably the blockade had an unexpected counter effect. Because the German chemical industry was so important, the Allies found themselves short of critical products — the French for example had relied on German chemicals for their shells and Britain imported almost 30,000 tons of dyes a year.
With lethal by-products coming as part of her daily industry it is not surprising that people thought of putting some of them to use.
Not all gases are instantly deadly nor are many of the more noxious ones intended to be. Even today we still witness tear gas being used on rioters. In some parts of the world pepper sprays can be legally obtained as a means of personal defence.
On a basic level it is necessary to understand the following.
Asphyxiating – a gas which attacks the lungs
Lachrymatory (tear gas) – it attacks the eyes and makes them water (Like chopped onions)
Vesicant – a gas which acts as a skin irritant, causing blisters etc.
Sternutatory – a gas which makes you sneeze
Toxic – a gas which attacks the body by passing into the blood stream
According to the actual gas and the dosage applied
some gases could fall into more than one category.
Another important property of each gas was its persistence.
A gas that has a low boiling point and mixes rapidly with the atmosphere is ideal for a localised effect for up to an hour — after which it will naturally disperse.
On the other hand a gas that has a high boiling point may rest as droplets over the terrain that has been targeted. It will only slowly dissolve into the atmosphere and will attack everything that touches it. This could mean that whilst the enemy may have to evacuate the ground it will not be possible to seize it.
In general, asphyxiating and toxic gases fall into the first group and lachrymatory and vesicant the latter.
Each gas has its level of danger; the point at which it will start to have an effect.
Tear gas: 10mg per cubic metre of air
Vesicant: 100 – 500mg per cubic metre
Asphyxiating: 500 – 2000mg per cubic metre
Even then the effect might not be readily noticeable and each gas by its nature dissipates over time. The location used and the climatic conditions would also have to be taken into account.
Releasing gas into a strong wind would merely disperse it — diminishing its effect.
The German scientist Fritz Haber carried out a great deal of research into the quantity necessary to render a gas lethal within 1 minute.
This is known as the Haber Rule.
He realised that a long exposure to a small dose had the same effect as a short exposure to a high dose — the effect is cumulative.
Ypérite, or mustard gas (vesicant): 1500mg per cubic metre
Chlorine (asphyxiating): 7500mg per cubic metre
Diphenylchloroarsine (sternutatory): 4000mg per cubic metre
Bromoacetone (lachrymatory): 4000mg per cubic metre
By using his research it was possible to calculate how much of each gas would be needed for a given area over a given period of time.
Thus; as an example:
If you wanted to make mustard gas lethal for an hour you would need to maintain
1500/60 = 25mg of the gas per cubic metre for the hour.