Question: What chemist created a viscous, colorless liquid used in World War I? 
Sentence (from "Sulfur mustard"): Sulfur mustard, commonly known as mustard gas, is the prototypical substance of the sulfur-based family of cytotoxic and vesicant chemical warfare agents known as the sulfur mustards which have the ability to form large blisters on exposed skin and in the lungs.
Relevant evidence: No