Life through the lens

In a new series exploring some of the characters behind the discoveries that shaped the modern world we find that a scientist’s legacy is shaped not just by the work they undertook, but by the lens of history

Thomas Midgley Jr has been credited with having not one but two discoveries which have had severe environmental consequences across the globe – meet the inventor of tetra-ethyl lead and chlorofluorocarbons

Thomas Midgley Jr was an American mechanical engineer turned chemist, son of a British-born inventor and graduate of Cornell University, and has “had more impact on the atmosphere than any other single organism in Earth’s history” according to historian John McNeill¹. Why? He invented tetra-ethyl lead and chlorofluorocarbons.

Midgley worked for General Motors and was charged with finding a solution to the irritating knocking experienced in car engines at the time; his answer was tetra-ethyl lead (TEL). He was also directed to find an alternative to the toxic and explosive chemicals used as refrigerants and came up with chlorofluorocarbons (CFCs). Unbeknown to him, both discoveries dealt harsh blows to the environment, but he died at the age of 55 before the damage became apparent.

In the early 20th century, cars suffered from terrible ‘ping’ and ‘putt-putt’ sounds; Midgley found a cure to this annoying problem –TEL or (CH3CH2)4Pb. The lead in TEL increased the fuel’s octane rating – the measure of resistance of a fuel to auto ignition in an internal combustion engine – preventing premature detonation and engine knocking.

TEL was only required in small quantities – it was mixed with petrol in the ratio 1:1260 – but it had undesirable effects on the engine. Carbon-lead bonds within TEL are weak and the temperature inside an internal combustion engine is enough to break the bonds and allow the chemical to decompose into lead, lead oxides and ethyl radicals. While the lead and lead oxides scavenged radical intermediates and prevented the ignition of unburned fuel, they also reacted with oxygen and destroyed the engine.

“Bromine was found necessary to the solution of one of those problems—that of preventing the formation of lead oxide during combustion and its deposition on valves and in the combustion space,” said Charles F Kettering in his autographical memoir of Midgley. “Since it appeared that for the purpose bromine would be needed in amounts much larger than had ever been available before, an intensive search was made for further supplies of it.”²

So Midgley set about hunting for an inexhaustible supply of bromine and subsequently discovered - and is credited with - how to extract bromine from seawater. The bromine was added to petrol in the form of 1,2-dibromoethane and was used to flush lead from the engine.

TEL was named ‘Ethyl’ and promoted as an alternative to ethanol or ethanol-blended fuel – on which General Motors could make little profit. It seems General Motors and Midgley – only too aware of the toxicity of lead – were careful to avoid any mention of the chemical in the name. Midgley himself suffered a case of lead poisoning following an attempt to demonstrate the safety of TEL. There had been several deaths and even more cases of lead poisoning at General Motors’ TEL production plants, so in a press conference he poured the chemical over his hands and placed a bottle of the chemical under his nose, breathing it in for 60 seconds. It was reported that he needed almost a year off to recover from his self-inflicted lead poisoning, and his demonstration did nothing to save the production plant – the State of New Jersey shut it down three days later.

Although only small amounts of TEL were required, lead’s impact on the environment is world-wide. It is dispersed through the air and is easily inhaled. It is neurotoxic and causes brain and blood disorders³, and studies in America suggest it caused low IQ and anti-social behaviour during the period of its use⁴.

In the early 1950s – several years after Midgley’s death – Clair Patterson

discovered the accumulative effect of lead in soil. He was trying to determine the age of the earth by measuring the lead content of the rocks but his readings were affected by lead contamination. After further investigation he discovered the lead contamination could be dated back to when TEL was first used and – realising the health and environmental effects of lead – he became one of the earliest opponents of its use.

Midgley was charged with developing a non-toxic and safe refrigerant for household appliances like fridges by a sub-company of General Motors. He came up with dichlorodifluoromethane or Freon as it was dubbed.  Midgley actually improved a process developed by Frédéric Swarts in the 1890s to synthesise CFCs, but he went further and led efforts to replace ammonia, chloromethane and sulphur dioxide with CFCs.

CFCs were exactly what Midgley had been asked to create – they were non-toxic, had low reactivity and low flammability and were used as refrigerants, blowing agents, degreasing solvents and as propellants in medicinal applications like inhalers. Midgley thought CFCs were completely safe – even inhaling the gas and blowing out a candle with it to illustrate its safety.

It wasn’t until after Midgley’s death the environmental effects of CFCs became apparent. Because they have very low reactivity – a lifespan of over 100 years – this gives them plenty of time to reach the upper stratosphere and ozone layer where ultraviolet radiation is known to break chlorine-chlorine bonds. This leads to highly reactive chlorine radicals which catalyse the breakdown of ozone into oxygen.

So Midgley played an important role in the development of two life-changing – and life-threatening chemicals – but others involved seem to have been forgotten. Both TEL and CFCs were developed under the guidance of his long-term colleague Charles Kettering (who is incidentally credited with the creation of a World War I aerial torpedo the Kettering bug).

But, Midgely should not just be remembered for these environmental

catastrophes. His scientific successes include discovering one of the first known catalysts – iron selenide – for cracking hydrocarbons to create aromatic versions, and he is also known for his investigative work on rubber. At the time rubber was high in price and in short supply and he studied the composition of natural and synthetic rubbers and the chemistry of vulcanisation.

“This work resulted in the publication of a series of nineteen outstanding papers. While nothing of a commercial character came of those researches, Midgley considered the work he did on rubber as the most scientific of all his endeavours,” Kettering said “And among those informed in the field he received a great deal of recognition for it.”

In the National Academy of Science Biographical Memoir of Thomas Midgley Jr, his long-standing colleague Kettering paints the picture of a conscientious but fearless and courageous worker, who never deterred from his current project. Midgley received many accolades for his work including several highly prestigious chemistry awards; the Nichols Medal, Edward Longstreth Medal and the Perkins and Priestley Medals. Shortly before his death he also received the Willard Gibbs Award and was elected to membership of the National Academy of Sciences.

Midgley was never to know of the devastating environmental effects of his most notorious work. In a cruel twist of fate he contracted polio in 1940 which left him severely disabled; he died in 1944 after becoming entangled and strangling himself in a system of pulleys and strings he had created to help others lift him from his bed – long before the devastating environmental effects of his discoveries were known.