The first commercial process proposed for the manufacture of mustard gas depended upon the use of ethylene chlorhydrin; and on April 13, 1918, a contract was made with the Commercial Research Co., Flushing, Long Island, for the manufacture of 10 tons per day by this process. In the spring and summer of 1918 a new process was developed both abroad and in the United States, one which used sulphur monochloride. Accordingly, the contract with the Commercial Research Co. was canceled, and efforts were concentrated on the later process.
This process consisted in blowing gaseous ethylene into liquid sulphur monochloride in large iron reaction vessels. The reaction developed much heat. Sulphur is set free by this reaction, and the temperature must be controlled in order to prevent the formation of solid sulphur in the reaction machine.
At the date of the armistice three mustard gas plants were either completed or nearing completion. The construction of the Edgewood plant was begun on May 18, 1918, and the first mustard was produced exactly a month later. The changing of processes, however, hampered production somewhat, but by September 20, the arsenal was producing 10 tons per day, and by November 11 had increased this to 30 tons per day. The total production of mustard gas at Edgewood during the war period was 711 tons, of which approximately 300 tons went into shell.
On July 8, 1918, the Government began the construction of a mustard gas plant at Hastings, N. Y. This factory was to have a capacity of 25 tons per day, afterwards increased to 50 tons per day. The first unit of this plant was ready to operate when the armistice was signed.
On July 6, 1918, the Government signed a contract with the National Aniline & Chemical Co., Buffalo, N. Y., calling for a mustard gas plant with a capacity of 50 tons daily. On November 11 this plant was 80 per cent complete. The cost of the plant was met by the Government, but the operation was to be in the hands of the Buffalo concern. The total daily capacity of all three plants when complete was estimated to be 200 tons.
To insure an adequate supply of sulphur monochloride for its mustard gas production the Government built a special plant at Edgewood with a capacity of 300 tons of sulphur monochloride per day.
As soon as toxic gas warfare had developed to a considerable extent, the perfection of gas-absorbing masks had given almost a complete protection against this new weapon, if the soldier put on his gas mask in time. But the mask, especially the earlier forms of it, was not easy upon the wearer, due to the difficulty of breathing through it and also because it restricted the soldier's vision. It was soon discovered that a force compelled to wear its gas masks for any considerable period lost in efficiency. The employment of gas by both sides for the purpose of forcing the opposite sides to wear masks continually was an important element in war at the close of hostilities.
For this purpose the so-called tear gases were produced. Gassing the enemy with tear gas was much cheaper than with poison gas, yet it forced him to remain masked. The tear gases were highly effective. Even a trace of tear gas in the air would in a few moments blind a man temporarily. A single tear-gas shell could force the wearing of masks over an area so wide that it would require from 500 to 1,000 phosgene shell to produce the same effect.
Most of the tear gases had bromine bases; so it was early determined that we should have to increase the American supply of bromine considerably if we were to meet our gas-warfare requirements. Bromine is a deep red liquid which boils at 63° C. The domestic source of bromine is principally in certain subterranean brines found in the United States, these solutions containing bromine in its compounds. The brines obtained in the vicinity of Midland, Mich., are especially rich in bromine, and by far the largest amount of bromine obtained in this country comes from that locality.