Reactions takes a look into chemical warfare. There's a lot of science behind chemical weapons. April 22, 2015 marks the 100th anniversary of the first large-scale use of chemical weapons in modern warfare. Some of the best minds in chemistry at that time, including a Nobel Prize winner, used their knowledge of science to build humanity’s new weapons of mass destruction. This week, we take a sobering look at the chemistry behind the modern world’s first chemical weapons.