Mustard Gas: Its Pre-World War I History

Mustard gas is perhaps the best-known chemical warfare agent and is commonly associated with World War I, both in its first use in warfare and its first synthesis. Although the former is correct, the latter is not. We review here the history of the repeated synthesis of mustard gas by 19th century European chemists. The techniques developed by these chemists were the ones relied upon by both the Central Powers and the Allies to manufacture this agent during World War I. Further, a historical review of mustard gas synthesis highlights the increasing sophistication of the chemical sciences. In particular, during the latter half of the 19th century, the concepts of atomic mass, chemical periodicity, and chemical structure underwent a rapid development that culminated in the application of quantum mechanics to chemistry in the 20th century. A comparison is made of the molecular formula for mustard gas from the 19th century with that of the 21st century, demonstrating that the concept of atomic mass has underg...