..... Stumper Index
Stumper #29.






How Good Is Your Science KQ?

[i.e. your Knowledge Quotient]

What About Air?

Most of what any scientist knows is based on accumulated wisdom derived over time from observations and deductions of others. We now know a lot about the chemical composition of the air surrounding our planet. What do we know about the early sequence of events that led up to the basis for our current knowledge?

Anxious to learn more about air during the mid to late 1700s, a handful of scientists in Europe focused mainly on burning things in air to discover how both the air and the burned substance were altered in the process. Investigators found that it seemed that air could be converted into a variety of forms and they typically spoke of different "airs."

In 1754, Joseph Black identified what he called "fixed air" because it could be returned, or fixed, into the sort of solids from which it was produced.

In 1772, Daniel Rutherford found that when he burned material in a bell jar, then absorbed all the "fixed" air by soaking it up with a substance called potash, a gas remained. Rutherford dubbed it "noxious air" because it asphyxiated mice placed in it.

Carl Wilhelm Scheele discovered in 1772 that red-hot manganese oxide produces a gas. He called the gas "fire air" and carefully recorded the experiment in his notes, but did not publish until 1777. In April 1774 Pharmacist Pierre Bayen discovered that heating mercury oxides resulted in a discharge of gas and a loss of mass. Bayen did not interpret his results and did not examine the gas further.

Later, in August 1774, Joseph Priestley declared that "air is not an elementary substance, but a composition," or mixture, of gases including a colorless and highly reactive gas he called "dephlogisticated air." Priestly hypothesized that this "air" allowed things to burn in it - without burning itself - because it had no phlogiston1 in it. He wrote, "What surprised me more than I can well express, was that a candle burned in this air with a remarkably vigorous flame..."

Then, Priestley met French scientist Antoine Lavoisier and described his discovery. This meeting and conversation gave Lavoisier the clue he needed to develop a revolutionary theory of chemical reactions that would show the phlogiston theory to be wrong. He deduced that Priestley's gas, which did not itself burn, had the property of encouraging - in the right circumstances - the combustion of other substances.

So, now we know some of the principle players in the early discovery of the composition of air. The stumper question is:
a) which one of these four: Scheele, Bayen, Priestley, or Lavoisier is acknowledged as the discoverer of oxygen and
b) which one gave the name oxygen to the gas that had been called an "air" when it was first identified?

1. Phlogiston was believed to be the part of air that caused combustion. It was thought to be a flammable gas that could caused other substances around it to burn while it also burned.

Ref.: "National Historic Chemical Landmarks" American Chemical Society Web Site

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