A use that was proposed toward the end of the war, and that will undoubtedly be made of the gas in the future, is to have it planted in drums in the ground and exploded when an enemy is attempting to advance. This would be a highly economic way to distribute great quantities of the material at the moment and in the place most heeded. It has even been proposed, and this would seem entirely feasible, to sprinkle certain of these areas with mustard gas by means of sprinklers attached to drums or even tanks mounted on trucks.
Just before the Armistice the German made another development in the use of mustard gas. Instead of the ordinary amount of explosive, which only fairly opened up the shell and allowed the liquid to escape, he filled nearly 30 per cent of the total space of the shell with high explosive. This completely broke up the shell and distributed the greater part of the liquid mustard gas in the form of a fine spray. This spray, when breathed, proved extremely deadly, as might be expected from the fact that when in the form of minute particles one can draw into the lungs in a single breath one hundred times or more the amount that he would get of pure gas.
Since mustard gas has such a delay action and is effective in such small concentrations it can be used very effectively in small calibre guns, as the 75 mm. or 3-inch. Furthermore, since it lasts for two or three days at the very least, a small number of guns can keep a very large area neutralized with the gas. With phosgene and similar non-persistent gases that volatilize almost completely upon the burst of the shell it is necessary to build up a high concentration immediately. The exact opposite is true of mustard gas. Mustard gas can be fired very slowly with the certain knowledge that all shells fired at one moment will be effective when the next is fired, though twelve hours or more may intervene between the first and last firing. Thus, while with phosgene a large number of guns are needed for a gas attack, with mustard gas the number can be reduced to one-tenth or even less. Mustard gas may be in the future and has been in the past used safely in hand grenades because of its very low vapor tension, whereby the pressure at ordinary temperatures is exceedingly low. This has an important bearing on cylinders and other containers for shipping mustard gas, that is, they need be only strong enough to be safe against handling and not to withstand the high pressure encountered with phosgene or chlorine cylinders.
In the future, mustard gas will be used in all the ways above stated and undoubtedly in many more. It can be fired in large quantities upon strong points to force their evacuation. It can be fired on the flank of attacking armies for protection against counter-attacks. It can be fired against the enemy artillery at all times to silence them and stop their firing. It was thus used by the Americans in the Argonne against the enemy on the east bank of the Meuse River, this river separating the American and German armies. It was extremely effective in stopping the enemy’s artillery. The high explosive mustard gas shell, not only because of its persistency but because of its quick deadliness, can be fired singly and be depended upon to do its work wherever there be men or animals. One of the greatest uses will be by simple sprinkling from aeroplanes.
The future will see mustard gas used at nearly all times with a certain quantity of a powerful lachrymator or tear gas. This is for the reasons, as stated in the beginning, that mustard gas causes no immediate discomfort and has no objectionable smell. Accordingly, if the battle be critical, men may continue to fight from four to eight hours in a mustard gas atmosphere without masks. It is true the casualties will be high with a high death rate. Nevertheless, this period of time might enable the artillery to do such effective work as to completely stop an attack. If, however, at the instant mustard gas firing is begun a number of powerful lachrymatory shells are sent over, the immediate wearing of the mask is forced. The enemy is then subject to all the burning effects of mustard gas as well as the discomfort of long wearing of the mask.
It may confidently be expected that further developments in the use of mustard gas will be made, as well as further developments in methods of throwing it upon the enemy or of bursting shell containing it in his midst.
CHAPTER X
ARSENIC DERIVATIVES
Since arsenic is well known as an insecticide in the form of lead arsenate, arsenic acid etc., and in pharmacy, specially in the form of salvarsan and neosalvarsan, it is not surprising that the Germans should have endeavored to discover an arsenic derivative which would be of value from the point of view of chemical warfare. Very early in the war persistent rumors were circulated that the Germans were to use arsine. These rumors led to the use of sodium permanganate in the canister, but as far as is known, no arsine was actually used. Another suggestion which received considerable attention from American workers was the use of arsenides, which might decompose under the influence of the atmospheric moisture with the liberation of arsine. Calculation of the amount of arsenide necessary to establish a lethal concentration of arsine showed, however, that there was no possibility of using the material on the field.
Because of the use of arsenic trichloride in the manufacture of organic arsenic compounds, a method of preparation was developed from arsenic trioxide and sulfur chloride or hydrogen chloride. It was also shown experimentally that the phosgene of the tail gas of phosgene plants might be converted into arsenic trichloride by reaction with arsenic trioxide. Charcoal is the catalyzer of this reaction.
Arsenic trichloride is also of interest because it was one of the constituents of the mixture vincennite, early used by the French. This was a mixture of hydrocyanic acid, stannic chloride, arsenic trichloride and chloroform. While extensively used at first, it was gradually replaced by phosgene.