Prof. Frank T. Edelmann
AvH Kolleg at Hobart, November 2015
The life and legacy of Thomas Midgley Jr.
Ladys and Gentlemen,
today I would like to tell you something about Thomas Midgley Jr. I assume that most
of you in the audience never heard this name. Thomas Midgley Jr. was an American
chemist and inventor, whose inventions continue to influence all of us today.
Thomas Midgley Jr. was born about 125 years ago, on May 18, 1889, in Beaver
Falls, Pennsylvania. His intention was to help mankind - but two of his greatest inventions
threatened life on earth. In the end he was killed by his last invention. In the following I
will tell you what kind of fatal inventions he made.
Thomas Midgley Jr. was born into a family of inventors, notably in the field of
automobile tires. He grew up in Columbus, Ohia, and graduated in 1911 as a mechanical
engineer from the famous Cornell University. During his time at Cornell he developed a
great interest in experimentation which was so characteristic for all of his further life.
In 1916, Midgley began working at General Motors under the direction of Charles
Kettering. A significant practical problem which he tackled at General Motors was the so-
called "knocking" of combustion engines. Midgley discovered that this noisy engine knock
could be stopped by adding certain chemical compounds to the gasoline. Such
compounds are called additives. At General Motors, a variety of additives were tested but
later discarded for various reasons. For example, testing of aniline as a fuel additive lead
to noxious odors of the car exhaust gases. The following picture shows Thomas Midgley
Jr. experimenting with an engine at Dayton Research Laboratories, a subsidiary of General
Finally, in 1921, Thomas Midgley Jr. discovered that tetraethyl lead (or TEL) acts as
an outstanding anti-knock agent in gasoline and leads to a greatly improved performance
of combustion engines. Thus he was the one who invented leaded gasoline! In December
1922, Midgley was awarded the Nichols Medal of the American Chemical Society for the
"Use of Anti-Knock Compounds in Motor Fuels". A major problem with this invention,
however, was the well-known high toxicity of lead. The chemical composition of
tetraethyl lead is Pb(C2H5)4:
This is a so-called organometallic compound of lead, which means that the lead
atom is directly bonded to carbon atoms. In this case we have four ethyl groups
connected to the lead atom. The physical properties of such organometallic compounds
are completely different from those of simple metal salts. For example, lead salts are
soluble in water and have high melting points. Therefore, lead salts are highly toxic when
swallowed, but they cannot easily pollute the atmosphere. The situation is completely
different when we turn to organometallic lead compounds such as tetraethyl lead.
Tetraethyl lead is a colorless liquid which is easily vaporized. This property of tetraethyl
lead was important for its possible use as fuel additive as it had to be miscible with the
gasoline. However, it had the severe disadvantage in that it could easily diffuse into the
atmosphere. Even after combustion in the automotive engine, large amounts of lead
particles were released into the atmosphere.
At that time, in the 1920's, it was well established that lead compounds are
dangerous nerve poisons or neurotoxins and can lead to irreparable damage of the
human brain and central nervous system. Workers producing the additive were exposed
to severe health hazards. Within the first two months of production, the new plant was
plagued by numerous cases of acute lead poisoning, accompanied by visual disorders,
hallucinations, insanity, and five deaths in quick succession. All this was accepted by the
industry. Too big were the promises of the new, cheap miracle cure for cars and airplanes.
Motors moved into gear much quicker and performed smoother than before the arrival of
TEL. Leaded fuel was first marketed in 1923. Midgley was not only a researcher but also a
successful businessman. He became the first General Manager of the newly created Ethyl
Gasoline Corporation, the company that produced and marketed tetraethyl lead.
The next picture shows a promotional sign for leaded fuel on a gasoline pump. It is
interesting to note that the full name tetraethyl lead was shortened to ethyl so that the
ominous term lead would not show up on the gasoline pump.
The next pictures show newspaper ads of the Ethyl Gasoline Corporation intended
to present leaded fuel in a positive light.
However, as mentioned earlier, the toxic effects of lead were generally known and
well established. As negative headlines continued, Midgley reacted with a drastic Public
Relations move to demonstrate the harmless nature and apparent safety of TEL: On
October 30, 1924, Midgley organized a press conference where, in the presence of
numerous journalists, he poured tetraethyl lead over his hands. He also placed a bottle of
the dangerous chemical under his nose and inhaled the vapor for 60 seconds. Then he
declared: "I could do this every day without getting any health problems whatsoever." In
saying this, Midgley consciously lied to the journalists. Shortly after the press conference,
he was diagnosed with serious lead poisoning that took more than a year to cure.
The next picture shows a historic photograph of an American gas station with an
advertisement for leaded fuel.
Notwithstanding the serious health risks, tetraethyl lead quickly captured the
market and by summer 1925, 1.1 billion liters of leaded fuel had been sold. It took until
the mid 1970s that the US began phasing out leaded gasoline. In the European Union,
leaded fuel was finally banned on January 1st of 2000.
With his second great invention, Thomas Midgley Jr. indeed revolutionized
everyday life around the world and perhaps even saved many human lives. He succeeded
in developing cheaper and, above all, safer refrigerators. In the late 1920s, compounds
like ammonia, methyl chloride, or sulfur dioxide were employed as refrigerants in air
conditioning and refrigeration systems. All these gases were either toxic, highly
flammable or even explosive. The smallest leakage could result in serious illness, injury or
It was Thomas Midgley Jr. who for the first time developed a gas that replaced the
numerous toxic or explosives substances previously used as refrigerants and made
refrigerators safe. His new refrigerant was non-toxic and not flammable. The name of this
magic gas is dichlorodifluoromethane. It was the first of the chlorofluorcarbons, better
known as CFCs. The CFCs form a class of chemical compounds in which some or all
hydrogen atoms in hydrocarbons are replaced by chlorine and fluorine atoms.
Dichlorodifluromethane is more commonly referred to as "Freon 12". It is derived from
methane, which has the composition CH4. In the next picture you can see that in Freon 12
two chlorine and two fluorine atoms are now bonded to the carbon instead of the four
The next picture shows Tomas Midgley Jr. demonstrating one of the new CFC
Once again, Midgley did not back off from taking personal risks to substantiate the
importance of his discovery. In 1930, he inhaled a lungful of Freon and then blew out a lit
candle to show the American Chemical Society that CFC was absolutely non-toxic and
non-flammable. CFCs soon became the refrigerant of choice and by 1950 more than 80
percent of American farms and more than 90 percent of urban homes had a CFC-cooled
refrigerator. Moreover, Freon 12 and other CFCs were phantastically successful in other
applications, such as air conditioning, fire extinguishers and as propellants in aerosol
spray cans. The Society of Chemical Industry awarded Midgley the Perkin Medal in 1937
for his work.
Midgley died three decades before the ozone-depleting and greenhouse gas
effects of CFCs in the atmosphere became widely known. In the year 1974, the American
scientists Mario Molina und Frank Rowland warned against the global threat originating
from the CFCs. The Montreal Protocol was signed in 1987 and in March 1988 DuPont
agreed to reduce and eliminate CFC production. The worldwide production of CFCs was
totally phased out by 2005.
In summary, Thomas Midgley Jr. made two inventions which had a fatal impact on
the Earth's atmosphere. At the time of his discoveries, Midgley was a highly esteemed
American national hero. He held two honorary degrees and in 1941 the American
Chemical Society gave him its highest award, the Priestly Medal. In 1944 he was elected
president of the American Chemical Society. William Lloyd Evans acknowledged his merits
with the words: "In a wonderful way Thomas Midgley Jr. made life more enjoyable. The
after-world will appreciate the enduring value of his research." Today, his legacy is seen
mostly critical. Midgley's inventions became an incarnation for the threats to our planet.
The historian John McNeill remarked that Midgley "had more impact on the atmosphere
than any other single organism in earth's history." This cartoon even shows him as the
"worst scientist ever".
In 1940, at the age of 51, Midgley contracted polio, which left him severely
disabled. This led him to devise an elaborate system of strings and pulleys to help others
lift him from bed. This system was the eventual cause of his own death when he became
entangled in the ropes of this device and died of strangulation at the age of 55. This
happened on November 2, 1944, in Worthington, Ohio. After all, Thomas Midgley Jr. was
a tragic figure. We are still living with the consequences of his inventions and will for
many years to come.