THESE THREE MEN, Carl Scheele (Sweden), Joseph Priestley (England), and Antoine Lavoisier (France) all claimed credit for the discovery of the element that we now call oxygen. Carl Scheele discovered fire air [oxygen] sometime before 1773. He produced the gas several ways. In one method, he reacted (using modern names) nitric acid with potash (KOH and/or K2CO3) which formed KNO3. Distilling the residue with sulfuric acid produced both NO2 and O2. The former was absorbed by limewater (saturated Ca(OH)2), leaving fire air. He also obtained fire air from strongly heating HgO and MnO2 and by heating silver carbonate or mercuric carbonate and then absorbing the CO2 by alkali (KOH):
AgCO3(s) Ag(s) + CO2(g) + O2(g)
On August 1, 1774 Joseph Priestley first prepared oxygen by directing the sun's light with a 12-inch diameter burning lens onto a sample of red mercurius calcinatus per se (now HgO). Thus, Priestley independently had discovered oxygen which he called dephlogisticated air. His explanation of the reaction using was:
mercurius calcinatus per se + heat yields quicksilver + dephlogisticated air
Today, we would describe the same reaction as follows:
HgO(s) Hg(l) + O2(g)
AgCO3(s) Ag(s) + CO2(g) + O2(g)
On August 1, 1774 Joseph Priestley first prepared oxygen by directing the sun's light with a 12-inch diameter burning lens onto a sample of red mercurius calcinatus per se (now HgO). Thus, Priestley independently had discovered oxygen which he called dephlogisticated air. His explanation of the reaction using was:
mercurius calcinatus per se + heat yields quicksilver + dephlogisticated air
Today, we would describe the same reaction as follows:
HgO(s) Hg(l) + O2(g)
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