December 9: GM engineer discovers leaded gasoline on this date in 1921

Thomas Midgley Jr. wasn't looking to change the world forever. The engineer and chemist was part of a team organized by General Motors looking for a way to keep gasoline from burning at the wrong time in engines — the "knock" that was powerful enough in 1920 to make it sound like a car would fall apart. On this date in 1921, Midgley discovered that tetraethyl lead could raise the octane of gasoline. While ethyl alcohol could do the same trick, GM could patent tetraethyl lead, and formed the Ethyl corporation to market its invention around the world. While it stopped knock, leaded gasoline ranks among the worst environmental disasters of the 20th century; as Jamie Kitman wrote in 2000, estimates suggest leaded gasoline lead to toxic lead poisoning in 68 million children in the United States alone. Midgley himself suffered from lead poisoning, and while workers involved in its production died, the marketing machine behind Ethyl never suggested the danger of what it was selling: