Diphenylcyanoarsine
Diphenylcyanoarsine, also called Clark 2 by the Germans, was discovered in 1918 by Sturniolo and Bellinzoni and shortly thereafter used like the related Clark 1 gas by the Germans for chemical warfare in the First World War. The substance causes nausea, vomiting and headaches. It can subsequently lead to e.g. pulmonary edema.