On This Day

Friday 9th December 1921

98 years ago

A young engineer at General Motors (GM) named Thomas Midgley Jr. discovered that when he added a compound called tetraethyl lead (TEL) to gasoline, he eliminated the unpleasant noises (known as "knock" or "pinging") that internal-combustion engines made when they ran. Midgley could scarcely have imagined the consequences of his discovery: For the next five plus decades, oil companies would saturate the gasoline they sold with lead, a deadly poison. In 1911, a scientist named Charles Kettering, Midgley's boss at GM, had invented an electric ignition system for internal-combustion cars that made their old-fashioned hand-cranked starters obsolete, making the driving of a fuelled auto available to more people. Unfortunately, as these GM cars became more common, more and more people noticed the problem that when heated up, the engines made an alarming racket. The problem, Kettering and Midgley eventually figured out, was that ordinary gasoline was too explosive for spark-ignited car engines due to low “octane”. To raise the fuel's octane level and make it less prone to detonation and knocking, Midgley wrote later, he mixed it with almost anything he could think of, from "melted butter and camphor to ethyl acetate and aluminium chloride...[but] most of these had no more effect than spitting in the Great Lakes." He found a couple of additives that did work, however, and lead was just one of them. Iodine worked, but producing it was much too complicated. Ethyl alcohol also worked, and it was cheap, however, anyone with an ordinary still could make it, which meant that GM could not patent it or profit from it. Thus, from a corporate point of view, lead was the best anti-knock additive there was.