Ice-nine

Ice-nine is a fictional material appearing in Kurt Vonnegut's novel Cat's Cradle. In the story, it is developed by the Manhattan Project for use as a weapon, but abandoned when it becomes clear that any quantity of it would have the power to destroy all life on earth. Ice-nine is supposedly a polymorph of water more stable than common ice (Ice I_h); instead of melting at 0 °C (32 °F), it melts at 45.8 °C (114.4 °F). When ice-nine comes into contact with liquid water below 45.8 °C (thus effectively becoming supercooled), it acts as a seed crystal and causes the solidification of the entire body of water, which quickly crystallizes as more ice-nine. As people are mostly water, this effect means ice-nine kills nearly instantly when ingested or brought into contact with soft tissues exposed to the bloodstream, such as the eyes. A global catastrophe involving freezing the world's oceans with ice-nine is used as a plot device in Vonnegut's novel.