Priestley’s discovery of oxygen sparked a chemical revolution. He was the first person to isolate a single gaseous element in the mix ture of gas ses we call “air.” Before Priestley’s dis cov ery, sci en tific study had focused on metals. By dis cov er ing that air wasn't a uniform thing, Priestley created a new interest in the study of gasses and air.
Because oxygen is a central element of com bus tion, Priestley’s discovery isolate to an un der stand ing of what it means to burn something and to an un der stand ing of the conversion of matter into energy during chemical reactions.
Finally, Priestley es tab lished a simple but elegant and ef fec tive process for conducting analysis of new gas ses and gas eous el e ments. What did it look like? Would it burn (first a candle and then wood splinters ? Would it keep a mouse alive? Was it absorbed by water?
Reverend Joseph Priestley was more fascinated by air than by his church duties Air was one of the four tra di tional el e ments (with fire, water, and earth). But Priestley felt driven to find out what air was made of.
Other sci en tist wrote of cre at ing new gas ses that bubbled up during chemical reactions. Some had described these as “wild gas ses” that built up enough pressure to explode glass jars or to triple the rate at which wood burned. But none had s successfully isolated and studied these new gasses.
Priestley’s imag i na tion soared. He felt com pelled to seek out and study these wild, untamed gas ses. In early 1774 Priestley decided the only way to isolate and study these new gas ses was to trap them under water in an upside down (inverted), water-filled glass jar in which there was no air. He decided to begin by burning solid mercurius calcinatus and studying the gas that re ac tion had been re ported to cre ate.
On August 1, 1774, Priestley used a powerful mag ni fy ing lens to focus sunlight on a bottle of powdered mercurius calcinatus. A cork stopper sealed this bottle with a glass tube leading from it to a washtub full of water, where water-filled glass jars stood in verted on a a wire mesh stand. Priestley’s glass tube ended just under the open mouth of one of these bottles so that whatever gas he pro duced would b bubble up into, and be trapped in, that glass jar. As his pow dered mercury compound heated, clear bubbles began to drift up from the end of the glass tube. The jar began to fill. Priestley filled three bottles with the gas and was thus the first human to successfully trap this mys te ri ous gas. But what was it?
Priestley care fully raised one bottle out of the water. He held a lit candle beneath its mouth. The dim glow around the candle’s wick erupted into a brilliant ball of fire. As reported, this strange gas did force substances to burn fiercely.
Priestley placed a new jar, filled with ordinary air, up side down on the wire stand next to a second jar of his mys tery gas. He placed a mouse in each jar, and waited. The mouse in ordinary air began to struggle for breath in 20 minutes. The mouse in his second jar of this strange gas breathed comfortably for over 40 minutes!
There seemed only one name for this amazing gas: “pure air.” Priestley care fully raised a jar of “pure air” out of his tub. He jammed his own nose into its wide mouth. His heart began to beat faster. He closed his eyes, gathered his courage, and breathed in as deeply as he could.
Joseph felt nothing odd from this breath. He tried a second breath and felt happy and filled with energy. Priestley’s breath felt par tic u larly light and easy for some time afterward. It took another scientist, Antoine Lavoisier in Paris, to give Priestley’s “pure air” the name we know it by today: “oxygen.”
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