It was especially important, therefore, when Green discovered that, if the reaction was carried out at 30°, the sulfur did not settle out but remained in “pseudo solution” in the mustard gas (Pope) or as a loose chemical combination of the monosulfide (mustard gas) with an atom of sulfur (Green). This material has all the physiological activity of the pure monosulfide, while the enormous technical difficulties of handling separated sulfur are entirely obviated by this method of manufacture. To carry out the reaction Levinstein, Ltd., devised the Levinstein “reactor.” The apparatus is shown in Fig. 29. The process consists essentially in bringing together sulfur chloride and very pure ethylene gas in the presence of crude mustard gas as a solvent at a temperature ranging between 30-35° C. A supply of unchanged monochloride is constantly maintained in the reacting liquid until a sufficiently large batch is built up. Then the sulfur monochloride feed is discontinued and the ethylene feed continued until further absorption ceases. By controlling the ratio of mustard gas to uncombined monochloride, the reaction velocity is so increased that the lower temperature may be used. The product thus obtained is a pale yellow liquid which deposits no sulfur and requires no further treatment. It is ready for the shell filling plant at once. The obvious advantage of this method led to its adoption in all American plants started for the manufacture of mustard gas (Edgewood, Cleveland and Buffalo). ETHYLENE It was known from the work of certain French chemists that in the presence of such a catalyst as kaolin, ethyl alcohol is dehydrated at an elevated temperature to ethylene. The process as finally developed by American chemists consisted essentially in introducing mixtures of alcohol vapor and steam, in the ratio of one to one by weight, into an 8-inch iron tube with a 3-inch core, in contact with clay at 500-600° C. The use of steam rendered the temperature control more uniform and thus each unit had a greater capacity of a higher grade product. The gaseous products were removed through a water-cooled surface condenser. One unit of this type had a demonstrated capacity of 400 cubic feet per hour of ethylene, between 92 and 95 per cent pure, while the conversion efficiency (alcohol to ethylene) was about 85 per cent. The Edgewood plant consisted of 40 such units. This would have yielded sufficient ethylene to make 40 tons of mustard gas per 24-hour day. The English procedure consisted in the use of phosphoric acid, absorbed onto coke. An American furnace was designed and built which gave 2,000 cubic feet per hour of ethylene, with a purity of 98 to 99 per cent. This furnace was not used on a large scale, because of the satisfactory nature of the kaolin furnaces. [Illustration: FIG. 30.—Experimental Installation for the Production of Ethylene by Kaolin Procedure. Capacity 400-600 cu. ft. Ethylene per hr.] SULFUR CHLORIDE