Geoscience Reference
In-Depth Information
CHAPter 3
Evolution of Oxygenic Photosynthesis
The race was on, but nobody really knew there was race, at least not at
first. The year was 1771 (or maybe 1772), and the Swedish pharmacist
Carl Wilhelm Scheele was very busy indeed. Having just begun as labo-
ratory assistant to the chemist Torbern Bergman of Uppsala, Scheele
was immersed in unraveling the mysteries of air. His real motivation,
however, was more boyish than this; he really wanted to understand the
nature of fire. Scheele admitted, “one could not form any true judgment
regarding the phenomena fire presents, without a knowledge of the air.”
1
At this time in the history of science, air was a truly remarkable and
mysterious substance. We can see this by hearing how Scheele himself
summarized its properties: “Air is that fluid invisible substance which
we continually breathe, which surrounds the whole surface of Earth,
is very elastic, and possesses weight.” In addition to these meager facts,
it had been demonstrated that air contained carbon dioxide, but other
than this, precious little was known. Part of the problem was that the
concept of chemical elements was just emerging, and those making up
the components of air had yet to be discovered. Another problem was
that the nature of air could not be decoupled from the popular (at the
time) phlogiston theory. Phlogiston was believed to be a colorless sub-
stance without mass, which was liberated by flammable substances as
they burned. Therefore, air became “phlogistated” when objects burned,
and flammable substances could no longer burn when sufficient phlo-
