Xylyl Bromide.—This was one of the early lachrymators, and was produced at Leverkusen in a plant with a maximum monthly output of sixty tons. Production began, according to a statement on the works, in March, 1915. Its case can be judged from the fact that this compound was used almost as soon as the first chlorine cloud attack at Ypres.
The Germans undoubtedly attached considerable importance to their brominated lachrymators. In this connection their persistent efforts to retain the bromine monopoly with their Stassfurt product and to crush the American industry before the war are significant. The success of these efforts certainly placed us in a difficult situation during the war, both with regard to production of drugs and lachrymators.
German bromine was associated with potash in the Stassfurt mineral deposits, whereas the American product was produced from numerous salt springs and rock salt mines. Although Germany had not succeeded in crushing the American industry, yet the outbreak of war found her in a predominant position, for her two chief opponents, France and England, were cut off from their supplies, which were German; and American production was of little use, owing to the great excess of demand over supply, and the manipulation of output by German agents in America. A possible source of bromine existed in the French Tunisian salt lagoons, whose pre-war exploitation had been considered by an Austrian combination. The French wisely developed a Tunisian bromine industry sufficient for their own needs, and, on different occasions, supplied us with small quantities. But the development of such an enterprise in time of war was a severe handicap.
Diphosgene or Trichlormethyl Chloroformate.—This substance was toxic, a lachrymator, and slightly persistent. It attained a maximum monthly Output Of 300 tons at Leverkusen, and about 250 tons at Hochst. This was not a simple compound to make, and had no direct relationship with the stable product of the peace-time industry. At the same time, it provides an example of the way in which general technique developed by the industry was rapidly used to master the new process. In particular their method of lining reaction vessels was of value here. The reaction occurs in two stages by the production of methyl formate and its subsequent chlorination. The methyl-formate plant was part of an existing installation, but the chlorination and distillation plant were specially installed.
Chlorpicrin.—This was mixed with diphosgene and used in the familiar Green Cross shell. The production was very readily mastered and attained the rate of 200 tons per month. Picric acid, chlorine, and lime were required, all three being normal raw materials or products of the industry. At Hochst no new plant was installed, the manufacture being carried out in the synthetic indigo plant.
Phenylcarbylamine Chloride.—This was used in German chemical shell, and was not particularly effective against us, although produced in large quantities by the Germans, in vessels used in peace time for a very common intermediate, monochlorbenzene. The ease of production of this substance may account for its use in large quantities by the Germans, in order to increase their gas shell programme.
Mustard Gas or Dichlordiethyl Sulphide.—This was prepared in four stages:
(1) Preparation of Ethylene—by heating alcohol with an aluminium oxide catalyst at 400'0 C.
(2) Preparation of Ethylene-chlor-hydrin, by passing ethylene and carbon dioxide into a 10 per cent. solution of bleaching powder at a temperature below zero centigrade, and subsequent concentration of the product to a 20 per cent. solution.
(3) Conversion of the chlor-hydrin into thiodiglycol by treatment with sodium sulphide.