The Allies were able, through warning of the impending use of phosgene, to furnish a means of protection against it. It was at this time that the P and the PH helmets were devised, the cotton filling being impregnated with sodium phenolate and later with a mixture of sodium phenolate and hexamethylenetetramine. This helmet was used until the Standard Box Respirator was developed by the late Lt. Col. Harrison.
Allies Adopt Gas
For a week or two the Allies were very hesitant about adopting gas warfare. However, when the repeated use of gas by the Germans made it evident that, in spite of what the Hague had to say about the matter, gas was to be a part, and as later developments showed, a very important part of modern warfare, they realized there was no choice on their part and that they had to retaliate in like manner. This decision was reached in May of 1915. It was followed by the organization of a Gas Service and intensive work on the part of chemists, engineers and physiologists. It was September 25, 1915, however, before the English were in a position to render a gas attack. From then on the Service grew in numbers and in importance, whether viewed from the standpoint of research, production, or field operations.
The Allies of course adopted not only chlorine but phosgene as well, since both were cheap, easy of preparation and effective. They felt during the early part of the War that they should adopt a substance that would kill instantly, and not one that would cause men to suffer either during the attack or through symptoms which would develop later in a hospital. For this reason a large amount of experimental work was carried out on hydrocyanic acid, particularly by the French. Since this gas has a very low density, it was necessary to mix with it substances which would tend to keep it close to the ground during the attack. Various mixtures, all called “vincennite,” were prepared,—chloroform, arsenic trichloride and stannic chloride being used in varying proportions with the acid. It was some time before it was definitely learned that these mixtures were far from being successful, both from the standpoint of stability and of poisonous properties. While the French actually used these mixtures in constantly decreasing quantities on the field for a long time, they were ultimately abandoned, though not until American chemists had also carried out a large number of tests. However, following the recommendation of the American Gas Service in France in December, 1917, no vincennite was ever manufactured by the United States.
Lachrymators
Almost simultaneously with the introduction of the gas wave attacks, in which liquefied gas under pressure was liberated from cylinders, came the use of lachrymatory or tear gases. These, while not very poisonous in the concentrations used, were very effective in incapacitating men through the effects produced upon their eyes. The low concentration required (one part in ten million of some lachrymators is sufficient to make vision impossible without a mask) makes this form of gas warfare very economical as well as very effective. Even if a mask does completely protect against such compounds, their use compels an army to wear the mask indefinitely, with an expenditure of shell far short of that required if the much more deadly gases were used. Thus Fries estimates that one good lachrymatory shell will force wearing the mask over an area that would require 500 to 1000 phosgene shell of equal size to produce the same effect. While the number of actual casualties will be very much lower, the total effect considered from the standpoint of the expenditure of ammunition and of the objectives gained, will be just as valuable. So great is the harassing value of tear and irritant gases that the next war will see them used in quantities approximating that of the more poisonous gases.
The first lachrymator used was a mixture of the chlorides and bromides of toluene. Benzyl chloride and bromide are the only valuable substances in this mixture, the higher halogenated products having little or no lachrymatory value. Xylyl bromide is also effective. Chloroacetone and bromoacetone are also well known lachrymators, though they are expensive to manufacture and are none too stable. Because of this the French modified their preparation and obtained mixtures to which they gave the name “martonite.” This is a mixture of 80 per cent bromoacetone and 20 per cent chloroacetone, and can be made with nearly complete utilization of the halogen. Methyl ethyl ketone may also be used, which gives rise to the “homomartonite” of the French. During the early part of the War, when bromine was so very expensive, the English developed ethyl iodoacetate. This was used with or without the addition of alcohol. Later the French developed bromobenzyl cyanide, C₆H₅CH(Br)CN. This was probably the best lachrymator developed during the War and put into large scale manufacture, though very little of it was available on the field of battle before the War ended. Chloroacetophenone would have played an important part had the War continued.
Disadvantage of Wave Attacks
As will be discussed more fully in the chapters on “The Tactics of Gas,” the wave attacks became relatively less important in 1916 through the use of gas in artillery shell. This was the result of many factors. Cloud gas attacks, as carried out under the old conditions, required a long time for the preliminary preparations, entailed a great deal of labor under the most difficult conditions, and were dangerous of execution even when weather conditions became suitable. The difficulties may be summarized as follows:
(1) The heavy gas cylinders used required a great deal of transportation, and not only took the time of the Infantry but rendered surprise attacks difficult owing both to the time required and to the unusual activity behind the lines that became, with the development of aeroplanes, more and more readily discerned.