Today, let's ask who discovered oxygen. The
University of Houston's College of Engineering
presents this series about the machines that make
our civilization run, and the people whose
ingenuity created them.
In the mid 18th century,
people thought air was inert -- that it didn't take
part in combustion. We know that the oxygen in air
reacts with other materials when they burn. But
18th-century chemists thought burning materials
were simply releasing an invisible fluid called
phlogiston, which caused heating. No one supposed
burning had anything to do with the air itself.
They didn't know the culprit was oxygen, which
makes up one fifth of air.
Oxygen was finally pinned down as a separate
element by three people in the 1770s: an English
cleric named Priestley; the French chemist
Lavoisier; and a Swedish pharmacist named Scheele.
Priestley isolated oxygen in 1774, but he thought
he had laughing gas. A year later he decided he'd
actually taken the phlogiston out of air. At the
same time, Lavoisier (who knew about Priestley's
work) also isolated oxygen. He took it to be very
pure air.
Two years later, Lavoisier realized that he'd
actually separated a component of air; but he
thought it came into existence only when the air
was heated. Meanwhile, the Swede, Scheele, had been
working quietly. He published a book called
Air and Fire just after Lavoisier's
final word on the matter. In it, he identified
oxygen as a separate part of air, based on work
he'd done before either Priestley or Lavoisier.
Historian Thomas Kuhn uses this muddle to explain a
problem that bedevils scientific discovery.
Squabbles over credit cloud the real nature of
discoveries. Should we credit Priestley, who
isolated oxygen and then went to his death thinking
it was something else? Should we credit Lavoisier,
who saw it was part of air, but didn't understand
its nature? And what about Scheele, who published
his work after that part of the game was over?
The fact is that oxygen couldn't really be
understood until scientists changed their whole
view of matter. Priestley started a scientific
revolution that wouldn't be finished until John
Dalton built oxygen into the atomic theory of
matter -- thirty years later. The idea that burning
meant new combinations of atoms was too great a
leap for any one person to make. The pieces of the
puzzle added up, and added up, until suddenly an
unexpected new picture came clear.
Oxygen wasn't just discovered. Oxygen as we
understand it today couldn't have been discovered
in 1770. Instead, a whole new science had to be
forged to accommodate it. Priestley, Lavoisier,
Scheele, Dalton -- each added new insights that
finally forced a major scientific revolution.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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