There is rather a definite relation between the concentration of the gas and the life of a canister at any given rate of flow. Many of these relations have been expressed by formulas of which the following is typical. At 32 liters per minute flow, C⁰˙⁹ × T = 101,840, in which C is the concentration and T the time.
Shell Filling
The empty shell, after inspection, are loaded on trucks, together with the appropriate number of “boosters,” which screw into the top of the shell and thereby close them. The trucks are run by an electric storage battery locomotive to the filling unit. The shell are transferred by hand to a conveyor, which carries the shell slowly through a cold room. During this passage of about 30 minutes, the shell are cooled to about 0° F. The cooled shell are transferred to shell trucks, each truck carrying 6 shell. These trucks are drawn through the filling tunnel by means of a chain haul operated by an air motor to the filling machine. Here the liquid phosgene is run into the shell by automatic machines, so arranged that the 6 shell are at the same time automatically filled to a constant void. The truck then carries the filled shell forward a few feet to a small window, at which point the boosters are inserted into the nose of the shell by hand. The final closing of the shell is then effected by motors operated by compressed air. The filling and closing machines are all operated by workmen on the outside of the filling tunnel.
Fig. 25.—Filling Livens’ Drums with Phosgene.
The filled shell are conveyed to the shell dump, where they are stored for 24 hours, nose down on skids, in order to test for leaks.
Tactical Use
Phosgene was first used in cloud attacks in December, 1915. These attacks continued for about nine months and were then gradually replaced, to a large extent, by gas shell attacks. Phosgene was first found in German projectiles in November, 1916. These shell were known as the D-shell. Besides pure phosgene, mixtures of phosgene and chloropicrin, phosgene and superpalite, and phosgene and diphenylchloroarsine have been found.
Fig. 26.—Interior of a Shell Dump.