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Oxygen
| Article
# : |
11669 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
9 / 1986 |
4,102 Words |
| Author
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William J. Cromie
William J. Cromie is a freelance writer and executive director
the Council for the Advancement of Science Writing. He lives
outside Chicago. |
The feeling of it to my lungs was not sensibly different from that of common air, but I fancied that my breast felt peculiarly light and easy for some time afterward… Hitherto only two mice and myself had the privilege of breathing it.
Joseph Priestely thus described, in 1774, the sensation of breathing pure oxygen. However, the English chemist did not know it was oxygen. He called it "dephlogisticated air" or air from which a substance known then as phlogiston had been removed. Named for the Greek word meaning "burned," phlogiston supposedly was liberated when a substance was consumed by fire. Priestley expressed surprise "that a candle burned in this air with a remarkable vigorous flame" and "a piece of red hot wood [was] consumed very fast."
Unknown to Priestley, Carl Scheele, a Swedish pharmacist, discovered oxygen two years before he did, and Scheele referred to it as "fire air."
Neither scientist realized that he had located the invisible, colorless, tasteless gas that makes possible life and fire. Neither knew that he had isolated an element that formed with the universe 10 or may be 15 billion years ago. And, probably, neither was aware of the profound impact the discovery would ultimately have on chemistry, as well as science, technology, and many other aspects of living.
Each had unknowingly come upon a major constituent of the planet on which he lived. Earth is the only known world swathed in a thick blanket of oxygen and nitrogen and inhabited by creatures who can breathe such a mixture. Oxygen makes up 23 percent of the weight of this breathable blanket. Earth is also the only known world with more than 70 percent of its surface covered by water, a mixture of 89 percent oxygen and 11 percent hydrogen. Below this water is solid crust of rock, the weight of which is almost 50 percent oxygen.
This oxygen is not free but bound up in compounds that form rocks, minerals, and soil. To free it, Scheele and Priestley heated compounds such as red oxide of mercury which decomposed the oxide and released the oxygen. Priestley performed this experiment on August 1, 1774, and published his findings shortly afterward. Scheele did his experiments about two years earlier, but he published the results after Priestley did. Because of this, many people still regard Priestley as the "discoverer" of oxygen.
At first, Priestely thought he had
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