thomas midgley

Thomas Midgley, Jr, was an American Engineer and latterly a Chemist whose contribution to science was almost impossibly unfortunate and regrettable, since he was responsible for possibly two of the most destructive inventions of the 20th century.

Midgley used a knowledge of chemistry and, in particular, the Periodic Table to make two significant developments – lead based anti-knock additives for internal combustion engines and chlorofluorocarbons (CFCs) as the working fluids in refrigerators. Both these developments were of enormous commercial importance at the time (the 1920s) and remained in use for over half a century.

His anti-knocking additive, tetraethyl lead, was used in petrol until it began to be phased out in the 1970s and was totally withdrawn in the UK in 2000. Lead and its compounds are neurotoxins, and studies suggested that the lead(IV) oxide given out by vehicles using leaded fuel was causing brain damage in children growing up in areas close to major roads. Lead also poisons the catalysts of cars using catalytic converters used to convert carbon monoxide, nitrogen oxides and unburned hydrocarbons in car exhausts into innocuous carbon dioxide, nitrogen and water. In fact, the dangers asociated with lead and its derivatives were well known at the time, and probably the reason that the corporations involved with the production of tetraethyl lead chose to call their new petrol additive simply 'ethyl'. Much more consumer friendly.

Not content with putting enough lead into the atmosphere to kill people for decades, he turned his hand to another problem. In the 1920's compounds such as propane, ammonia, sulfur dioxide and chloromethane were used as refrigerant gases. All had disadvantages such as toxicity, flammability or chemical reactivity. One refrigerator leak in a hospital in Cleveland in 1929 killed over 100 people. What was required was a non-toxic, non-flammable, chemically inert gas/volatile liquid. In 1928, Midgley was called in to help with the search and with an instict for the regrettable that was almost uncanny, Thomas Midgley invented chloroflourocarbons, CFC's.

With a degree of showmanship, Midgley even demonstrated the suitable properties of his new discovery at a meeting of the American Chemical Society by inhaling some of the gas and then exhaling onto a lighted candle, which was extinguished.

CFCs went on to be an important commercial success, being used for several decades as refrigerator fluids and deoderant propellants. We now know that the chemical inertness of the CFCs (due in part to their strong C-F bonds) held the seed of a major environmental problem. On release into the atmosphere, CFCs do not break down and a large ‘reservoir’ of them built up in the atmosphere. However, high in the atmosphere they do decompose under the action of ultraviolet light, leading to the formation of chlorine radicals which catalyse the breakdown of ozone to oxygen. Since ozone absorbs ultraviolet radiation from the Sun, this leads to a greater intensity of UV radiation at the Earth’s surface causing problems such as increased rates of skin cancer, cataracts in the eyes, the death of plankton and faster decomposition of rubber, plastics and dyes. This began to be understood in the 1970s and CFCs have been withdrawn since the Montreal Protocol of 1987.

Although is easy to deride Midgley as being responsible for two major environmental catastrophes this is, of course, with hindsight. At the time both tetraethyl lead and CFCs were major scientific and economic breakthroughs and their consequences a half a century later simply could not have been predicted by Midgley or anyone else.

Finally, there is the bizarre tale of Midgley’s tragic end. In 1944, at the age of 51, Midgley contracted polio and lost the use of his legs. Using his engineering skills he devised a pulley system to enable him to get out of bed, which worked well until one day he became entangled in the ropes and was strangled.