Zyklon B (German pronunciation: [tsykloːn ˈbeː]; anglicized /ˈzaɪklɒn ˈbiː/ or translated Cyclone B) was the trade name of a cyanide-based pesticide invented in Germany in the early 1920s. It consisted of hydrogen cyanide (prussic acid), a warning eye irritant, and one of several adsorbents such as diatomaceous earth.