Hello, and welcome to HistoryPod. On 9 December 1921 Thomas Midgeley Jr. discovered
that adding tetraethyl lead to gasoline reduced knocking in automobile engines. Engine knock, sometimes referred to as ‘pinging’,
is caused by the improper timing of fuel combustion in an engine’s cycle. By occurring too early, the explosive ignition
causes a shock-wave that can cause serious damage to the engine cylinder. Thomas Midgeley Jr. was a mechanical engineer
at the US automobile manufacturer General Motors, where he was tasked with finding a
way to prevent engine knock. Although he had already found that mixing
gasoline with ethanol would reduce knock by raising the octane level of the fuel, it was
a process that was impossible to patent and thus make any significant profit from. Midgeley continued his search for a suitable
additive and on 9 December 1921, after working through thousands of chemicals, he finally
identified tetraethyl lead. Ignoring the dangers that this neurotoxin
presented, leaded gasoline soon became a standard feature on forecourts across the world while
the additive itself became known as TEL under the brand name Ethyl. A few months after his discovery, Midgeley
had to take time away from the laboratory due to lead poisoning. Some of his colleagues were not as lucky. Within a year ten workers at the lead plant
had died, while dozens more experienced neurological symptoms including tremors, hallucinations
and fits. Despite these evident dangers, leaded gasoline
continued to be the standard fuel for automobiles until it was ordered to be phased out in the
1970s. Midgeley himself later went on to develop
the first CFCs, making him the creator of two products that have caused serious long-lasting
damage to both human health and the environment.