June 17, 1918 - chemical weapons

While Mary finally applies for a job at the Eddystone Rifle Plant of the Midvale Steel and Ordnance Company, there is the following article on page 4 of the Evening Public Ledger:

Various irritant gases were used at the beginning of World War I in Europe, but the big three that caused the most injuries and deaths were chlorine, phosgene and mustard gas.  The Allies first started using mustard gas against the Germans in June 1918, likely the gas referred to in the newspaper article.

A detailed history of the use of chemical weapons, including a bio of Nobel prize winner Fritz Haber, largely responsible to the militarization of chemicals in World War I by the Germans, can be found at the Science History Institute web site.