Thomas Midgley - man of ideas
The job of an industrial chemist involves solving problems. Born in
1889, Thomas Midgley did an engineering PhD at Cornell University, and
in 1916 joined Charles Kettering's Lab in Dayton, Ohio. Midgley was
a very good industrial chemist, solving some of the most difficult chemical
problems of his day.
But the solutions he found left some rather awkward problems for everyone
who followed him …
The 'knocking' problem
Kettering was marketing a small kerosene engine to drive home-lighting
systems on farms. The problem with this engine was that the fuel in
it did not burn properly, sometimes igniting as the piston in the cylinder
was compressing the mixture of fuel and air, making the engine "knock".
Kettering asked Midgley to search for something that could be added
to the fuel to make it less volatile. This would make it less likely
to ignite under compression, and so less prone to knocking. Midgley
had the idea that dyeing the fuel red might cause it to absorb more
heat and knock less. This wasn't very good physics, and didn't work
for the reasons he had suggested - but when he mixed the kerosene with
iodine, there was definitely less knock.
After a few more random attempts to find suitable chemicals, Midgley
decided it was time to be systematic in his search for a better antiknock
additive :
In the course of my education I had occasion to learn
about the Periodic table and to have it impressed on my memory as
a very useful tool in research work … we abandoned the method
of trial and error in favour of a procedure based on the Periodic
Table. Predictions began fulfilling themselves instead of fizzling
out …
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Midgley began working systematically through the Periodic Table,
and the results from his experiments began to fall into a pattern.
Tellurium showed great promise for halting premature ignition,
but smelled strongly of garlic. If the tiniest amount was absorbed
by the skin it gave out an overpowering stench which couldn't
be removed for days. Defeated by the smell, the researchers gave
up and tried something else!
The results they got pointed to a solution at the heavy end of
the carbon group of the Periodic Table: silicon, germanium, tin
and lead. It got very exciting - when Midgley visited his father
in Massachusetts in late October, he had the antiknock results
from each new test sent via telegraph daily so he didn't miss
anything. Tetraethyl tin proved effective, but even more exciting
was the prospect of metallic lead at the bottom of the group of
the Periodic table.
When the chemists finally delivered a small amount of tetraethyl
lead on the morning of December 9, 1921, the one-cylinder laboratory
engine ran silently - the knocking had completely gone. Even greatly-diluted
the new compound tetraethyl lead had a remarkable ability to suppress
knocking in the engine. After six years of searching Midgley had
found his antiknocking compound.
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Thomas Midgley with the single cylinder laboratory
engine used to test fuel additives. |
Frightening fridges
Midgley took only three days to make his second great contribution
to science. The early refrigerators used unpleasant chemicals chemicals
like sulphur dioxide and ammonia as refrigerants. When these leaked
out, as they often did, they killed people. Midgley was commissioned
to find a better refrigerant. Once again he went back to his old friend
the Periodic Table and developed Freon. The name Freon covers several
different chemical compounds, each containing a combination of carbon,
chlorine and fluorine - a group of compounds now known as CFCs. When
Midgley presented Freon to the American Chemical society, he breathed
in the gas and then exhaled it gently over a candle flame - which went
out. In this single demonstration he showed that his new compound was
both non-toxic and non-flammable. Freon was excellent at its job and
safe to use - so it became widely used all over the world for many years.
Thomas Midgley trouble
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ctivity
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