Today, a murder inquest, and a serpentine ring,
touch a young man's mind. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
Physicist Hans von Baeyer
tells a strange story about the benzene molecule.
It begins in 1850 with a young architecture
student, Friedrich Kekule, testifying before a
grand jury in Giessen, Germany. The charred body of
a neighbor lady had been found in her room. People
thought she'd been the victim of spontaneous
combustion, brought on by drinking too much liquor.
The great chemist Justus von
Liebig testified at the trial. He made it quite
clear that the lady would have died long before
she'd drunk enough alcohol to make her flammable.
Then Kekule's testimony incriminated a servant
who'd been stealing from the lady. He identified
her distinctive ring, which turned up in the
servant's possession. Together, Liebig's and
Kekule's testimony convicted the scoundrel of
murdering the lady.
The trial left its mark on the young Kekule. He
gave up architecture and took up the study of
chemistry with Liebig. The lady's odd ring also
lingered in Kekule's mind -- it had carried the old
alchemy seal of two intertwined serpents biting
each other's tail.
Fifteen years later, Kekule worked with Liebig on a
new chemical called benzene. Logic dictated that it
must be an arrangement of six carbon, and six
hydrogen, atoms. But how could you arrange such a
molecule without violating the rules of chemical
valence? It didn't seem possible.
Kekule dozed in his chair by the fire, trying to
solve the riddle. As he nodded, he dreamt of the
twining serpents on that old ring, whirling in the
flames. Suddenly, in the dream, the serpents caught
each other's tail and formed a circle. Kekule saw
the answer. The carbon atoms formed an hexagonal
ring with alternating single and double bonds. Each
one held its own hydrogen atom -- "like charms on a
bracelet," says von Baeyer. It was a structure
utterly alien to anything else in chemistry.
We're seldom given such a clear account of the
moment an idea reveals itself. But in this case the
author's great-grandfather worked with Kekule and
handed down a rare insight. We're shown two
features of inventive thought: One is that the
inventor can bring outside abilities to a field.
Kekule had an architect's spatial and structural
sense -- a place to stand outside of chemistry --
another way to look at things.
But he was also able to place a problem in his
subconscious mind and turn his dreams loose on it.
Pure invention breaks the thread of logic. It
arises where we least expect it. Pure invention is
the fruit of recognition rather than deduction.
I'm John Lienhard at the University of Houston,
where we're interested in the way inventive minds