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August 1, 2025 3 mins
On August 1st in Science History, a significant event took place in 1774 when Joseph Priestley, an English chemist, theologian, and philosopher, discovered oxygen gas. This groundbreaking discovery revolutionized our understanding of chemistry and paved the way for numerous scientific advancements.

Priestley's discovery occurred while he was experimenting with mercuric oxide (HgO) and focusing sunlight onto it using a 12-inch "burning lens." He noticed that the gas emitted from the heated mercuric oxide could reignite a glowing ember, which had been extinguished moments before. Intrigued by this observation, Priestley conducted further experiments and found that a mouse could survive longer in this gas compared to ordinary air. He also noted that the gas could support combustion better than regular air.

Initially, Priestley called this gas "dephlogisticated air," based on the prevalent phlogiston theory of combustion at the time. However, it was later renamed "oxygen" by Antoine Lavoisier, a French chemist who recognized its true nature and role in combustion.

Priestley's discovery of oxygen had far-reaching implications across various scientific disciplines. In medicine, it led to a better understanding of respiration and the role of oxygen in sustaining life. This knowledge eventually led to the development of oxygen therapy, which has saved countless lives. In chemistry, the discovery of oxygen helped debunk the phlogiston theory and laid the foundation for modern chemical principles, such as the law of conservation of mass and the understanding of chemical reactions.

Moreover, Priestley's work on gases extended beyond oxygen. He also identified and isolated other gases, including ammonia, sulfur dioxide, and nitrogen dioxide. His pioneering work in pneumatic chemistry earned him the prestigious Copley Medal from the Royal Society in 1773.

Priestley's scientific contributions were not limited to chemistry. He was a polymath who made significant contributions to various fields, including electricity, optics, and political philosophy. He was a strong advocate for religious tolerance and freedom of speech, which often put him at odds with the established authorities of his time.

In conclusion, Joseph Priestley's discovery of oxygen on August 1st, 1774, stands as a pivotal moment in the history of science. His work not only revolutionized our understanding of chemistry but also laid the foundation for numerous scientific and medical advancements that have shaped our modern world. Priestley's legacy as a brilliant scientist, philosopher, and advocate for human rights continues to inspire generations of scientists and freethinkers alike.


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Episode Transcript

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Speaker 1 (00:00):
Welcome to This Moment in Science History podcast on August first.
In science history, a significant event took place in seventeen
seventy four when Joseph Priestley, an English chemist, theologian, and philosopher,
discovered oxygen gas. This groundbreaking discovery revolutionized our understanding of
chemistry and paved away for numerous scientific advancements. Priestley's discovery

(00:24):
occurred while he was experimenting with mercuric oxide HGO and
focusing sunlight onto it using a twelve inch burning lens.
He noticed that the gas emitted from the heated mercuric
oxide could re ignite a glowing ember, which had been
extinguished moments before. Intrigued by this observation, Priestley conducted further

(00:46):
experiments and found that a mouse could survive longer in
this gas compared to ordinary air. He also noted that
the gas could support combustion better than regular air. Initially,
Priestley called this gas dephlogisticated air, based on the prevalent
phlogistin theory of combustion at the time. However, it was
later renamed oxygen by Antoine Lavoisier, a French chemist, who

(01:10):
recognized its true nature and role in combustion. Priestley's discovery
of oxygen had far reaching implications across various scientific disciplines.
In medicine, it led to a better understanding of respiration
and the role of oxygen in sustaining life. This knowledge
eventually led to the development of oxygen therapy, which has

(01:31):
saved countless lives. In chemistry, the discovery of oxygen helped
debunk the phlogistin theory and laid the foundation for modern
chemical principles such as the law of conservation of mass
and the understanding of chemical reactions. Moreover, Priestley's work on
gases extended beyond oxygen. He also identified and isolated other gases,

(01:53):
including ammonia, sulfur dioxide, and nitrogen dioxide. His pioneering work
in numatat chemistry earned him the prestigious Coplly Medal from
the Royal Society in seventeen seventy three. Christly's scientific contributions
were not limited to chemistry. He was a polymath who
made significant contributions to various fields, including electricity, optics, and

(02:16):
political philosophy. He was a strong advocate for religious tolerance
and freedom of speech, which often put him at odds
with the established authorities of his time. In conclusion, Joseph
Priestley's discovery of oxygen on August first, seventeen seventy four
stands as a pivotal moment in the history of science.
His work not only revolutionized our understanding of chemistry, but

(02:38):
also laid the foundation for numerous scientific and medical advancements
that have shaped our modern world. Priestley's legacy as a
brilliant scientist, philosopher, and advocate for human rights continues to
inspire generations of scientists and freethinkers alike. And that wraps
it up for another episode. Please subscribe and join us
tomorrow for another great moment in science. This has been

(03:00):
a quiet Please Studios Production. For more check out Quiet
Please dot a I Thank you for listening.
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