Stability to Atmospheric and Chemical Agencies

From the chemical point of view a war gas must be sufficiently resistant to the various agents into which it may come into contact in practice. It is especially important that it should be indifferent to atmospheric agencies. In the first place, all these substances must be indifferent to atmospheric oxygen. However, a large number are decomposed more or less rapidly by the action of atmospheric humidity, and almost all are decomposed in time by rain. 

Rona has made some experiments on the decomposition of war gases by water. He has demonstrated experimentally that some substances are rapidly decomposed by water (phosgene, 

Chlorovinyl dichloroarsine is rapidly hydrolysed by water. According to Vedder 1 this substance, though powerfully toxic, could not be efficiently used in open country because of its high velocity of hydrolysis. 

In general, oxygen-containing compounds are more stable than the corresponding sulphur-containing ones, according to Meyer, who adds that the stability increases with an increase in the length of a chain of carbon atoms. 

With respect to their employment in war a knowledge of the behaviour of substances towards water is of great importance, particularly by rendering it possible to define the conditions of humidity in which a certain substance may be employed, especially in considering the length of time during which it is desired to maintain an area in the gassed condition. 

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