Geoscience Reference
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(a)
(b)
Figure 1.17.
(a) Joseph Priestley (1733-1804). (b) Reconstruction of Priestley's oxygen apparatus. Edgar Fahs
Smith Collection, University of Pennsylvania Library.
removed. Burning mercuric oxide in a vacuum released
oxygen so that it was the only gas in the container. Due
to the container's high oxygen content, flammable mate-
rial burned more readily in the container than in regular
air. He also found that the gas was insoluble in water,
supported combustion, and “invigorated a mouse.”
Priestley called the new gas, discovered August 1,
1774, “
dephlogisticated air
” because he incorrectly
believed that the gas burned so brightly because it con-
tained no phlogiston. He believed that the burning of a
substance emitted phlogiston, causing the flame to die
out eventually.
Scheele independently isolated molecular oxygen in
at least three ways: heating manganic oxide [Mn
2
O
3
(s)]
(a black powder), heating red mercuric oxide [HgO(s)],
and heating a mixture of nitric acid [HNO
3
(aq)] and
potassium nitrate [KNO
3
(s)].
Shortly after his discovery of oxygen in August 1774,
Priestley went on a tour of Europe. One of his stops was
in Paris, where he met Lavoisier.
Antoine-Laurent de
Lavoisier
was born into a wealthy French family on
August 26, 1743, in Paris. He studied chemistry, botany,
astronomy, and mathematics at the College Mazarin
from 1754 to 1761. His early scientific work was on
street lighting, for which he was admitted to the French
Academy of Sciences at age twenty-five, and on geolog-
ical surveying. In 1771, at twenty-eight, he married the
thirteen-year-old daughter of one of the coowners of the
Ferme Generale, an agency that set and collected taxes
for the king of France from 1726 to 1790. Lavoisier
became a member of the group, setting himself up for
his ultimate demise.
Lavoisier experimented with combustion and, on
November 1, 1772, found that phosphorus and sul-
fur weighed more after than before they were burned.
The reason, although he did not know it at the time,
wasthat both reacted with oxygen during combustion
by 4P(s)
+
fire
+
5O
2
(g)
→
P
4
O
10
(s) and S(s)
+
fire
+
O
2
(g)
SO
2
(g), respectively. In early 1774, he also
discovered that lead and tin weighed more and con-
sumed one-sixth to one-fifth of the volume of air when
they were burned. Again, he did not yet realize that
oxygen comprised about 21 percent of air and was con-
sumed during combustion.
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