NATURAL RESOURCES—LITTLE. 228 
Chloropicrin also played an important part in gas warfare and 
was produced at Edgewood to the amount of 2,320,000 pounds, the 
maximum amount actually produced in one day reaching 31 tons. 
It is made by treating calcium picrate with bleaching powder and 
steam and thus involves as ultimate raw materials limestone for 
making lime, benzol produced from coal in by-product coke ovens, 
and nitric and sulphuric acids for effecting the conversion of benzol to 
picric acid. Coal is again, of course, involved in the production of 
steam, and for the bleaching powder we have to turn once more to 
limestone for the lime and to chlorine resulting from the electrolysis 
of salt. 
Perhaps the most generally effective of all the substances used in 
gas warfare was dichloroethylsulphide, or mustard gas, produced by 
blowing gaseous ethylene into liquid sulphur monochloride. Ethy- 
lene is a product of the destructive distillation of coal in gas works, 
but in this case was made by passing alcohol over hot kaolin. Sul- 
phur is, of course, a basic resource, and, again, the chlorine comes 
through the electrolytic decomposition of common salt. 
At the date of the armistice Edgewood was making 30 tons a day 
of mustard gas and other great plants were building—all to a total 
daily capacity of 200 tons. The military importance of the material 
may be judged by the fact that at one time proposals were under dis- 
cussion for an output of 1,400 tons a day. 
Since the Germans introduced mustard gas, it is pleasant to be able 
to say that we ultimately greatly outdistanced them not only in the 
efficiency of the process itself, but in the amount and rate of produc- 
tion, which last was finally ten times that of Germany. 
As the wearing of a gas mask, particularly of the earlier types, 
greatly reduced the efficiency of troops and tended to lower their 
morale, substances which forced the wearing of the mask proved 
highly effective. They were known as tear gases and involved bro- 
mine as an essential constituent. Our domestic source of bromine is 
certain subterraneous brines, especially those about Midland, Mich., 
and a bromine plant was built with an annual capacity of 650,000 
pounds of this element. 
The tear gas adopted by us was brombenzyl cyanide, and a single 
shell thus loaded could force the wearing of masks over an area so 
extensive that from 500 to 1,000 phosgene shells would be required 
for the same effect. The compound itself was made by chlorinating 
toluol, thereby forming benzyl chloride, which was mixed with sodium 
eyanide in alcoholic solution and distilled with the production of 
benzyl cyanide. Finally, this was treated with bromine vapor. Thus 
the production of this single compound involves the electrolysis of 
salt to obtain chlorine, the distillation of coal for toluol, the bringing 
