When the charge was completed, the ethylene was turned off so that only a small amount bubbled through the nozzles and the charge syphoned off to the settling tank. These were constructed of iron, 8 feet in diameter and 19 feet tall. They were provided with iron coils by which the liquid may be cooled down, or the sulfur, which precipitates in the bottom, melted. The tank was large enough to hold six complete charges of mustard gas and all the sulfur from these charges was allowed to accumulate before removal of the sulfur. The supernatant mustard gas was drawn off from above this sulfur to storage tanks. Among the factors which influence the reaction are the following: A temperature of over 60° C. in lead will decompose the product slowly when sulfur chloride is present. The presence of iron decomposes the product rapidly at a temperature of 50° C. and probably at a considerably lower temperature. The purity of the product is dependent upon the time of reaction. There is always a slow reaction between the mustard gas and sulfur chloride, and because of this the charge should be completed in 8 hours. In general the more sulfur that comes out of the solution, the better is the product. Temperature has a marked effect on the separation of sulfur. In order to entirely remove the sulfur from the product it was the custom to increase the temperature at the close of the reaction from 55° to 70° C. This, however, caused plugging of the lines and the reactor. PROPERTIES Dichloroethylsulfide (mustard gas) is a colorless, oily liquid, which has a faint mustard odor. The pure material is said to have an odor very suggestive of that of water cress. While the odor is more or less characteristic, it is possible to have extremely dangerous amounts of the gas in a neighborhood without being detected through its odors. It still seems to be an open question whether mustard gas paralyzes the sense of smell. One can find opinions on both sides. Mustard gas boils at 215°-217° C. at atmospheric pressure, so that it is at once seen to be a very persistent gas. It distills without decomposition at this temperature but is best purified by vacuum distillation, or by distillation with steam. A still for the vacuum distillation of mustard gas has been described by Streeter.[20] [Footnote 20: _J. Ind. Eng. Chem._, 11, 292 (1919).]