Following the Path of Discovery
Repeat Famous Experiments and Inventions
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Everyone needs oxygen to survive – man and animals alike. Furthermore, oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere. Oxygen accounts for nearly half of the mass of the earth's crust, two thirds of the mass of the human body and nine tenths of the mass of water.
In this page we will try to outline the path to the discovery of this important substance.
Oxygen was discovered for the first time by a Swedish Chemist, Carl Wilhelm Scheele, in 1772. Joseph Priestly, an English chemist, independently, discovered oxygen in 1774 and published his findings the same year, three years before Scheele published. Antoine Lavoisier, a French chemist, also discovered oxygen in 1775, was the first to recognize it as an element, and coined its name "oxygen" - which comes from a Greek word that means “acid-former”.
There is a historic dispute about who discovered oxygen. Most credit Priestly alone or Both Priestly and Scheele. To learn more about this dispute go to the link section, at the bottom of this page.
In 1772, Carl Wilhelm Scheele discovered that red-hot manganese oxide produces a gas. He called the gas "fire air" because of the brilliant sparks it produced when it came in contact with hot charcoal dust. He repeated this experiment by heating potassium nitrate, mercury oxide, and many other materials and produced the same gas. He collected the gas in pure form using a small bag. He explained the properties of “fire air” using the phlogiston theory, which was soon discredited by Lavoisier. He carefully recorded his experiments in his notes, but waited several years before publishing them.
In 1774, Priestley repeated Scheele’s experiments using a 12-inch-wide glass "burning lens", he focused sunlight on a lump of reddish mercuric oxide in an inverted glass container. The gas emitted, he found, was "five or six times as good as common air." (1) In succeeding tests, it caused a flame to burn intensely and kept a mouse alive about four times as long as a similar quantity of air.
Priestley, a big supporter of the phlogiston theory, called his discovery "dephlogisticated air" on the theory that it supported combustion so well because it had no phlogiston in it, and hence could absorb the maximum amount during burning.
Repeat Scheele’s and Priestley experiments:
Warning: Heating up materials and breathing vapors could be very dangerous. As a rule: this experiment should be performed under the supervision of teachers or adults familiar with safety procedures. Consult your teacher or other knowledgeable adults and experts about how to obtain the mentioned materials and how to use them properly and safely in this experiment. Do not do this experiment alone!
Consult the link section and further resources provided. Ensure that you understand the basic principals. Surf the web and consult your local library, your teacher and other knowledgeable adults and experts.
In August of 1771, Joseph Priestley, put a sprig of mint into a transparent closed space with a candle that burned out the air until it soon went out. After 27 days, he relit the extinguished candle again and it burned perfectly well in the air that previously would not support it. And how did Priestley light the candle if it was placed in a closed space? He focused sun light beams with a mirror onto the candle wick (Priestley had no bright source of light, and had to rely on the sun). Today, of course, we can use more sophisticated methods to light the candle like focusing light from a flood light through converging lens, or by an electrical spark.
So priestly proved that plants somehow change the composition of the air.
In another celebrated Experiment from 1772, Priestley kept a mouse in a jar of air until it collapsed. He found that a mouse kept with a plant would survive. However, we do not recommend to repeat this experiment and hurt innocent animals.
These kinds of observations led Priestley to offer an interesting hypothesis that plants restore to the air whatever breathing animals and burning candles remove - what was later coined by Lavoisier "oxygen".
In these experiments, Priestly was the first to observe that plants release oxygen into the air - the process known to us as photosynthesis.
Repeat Joseph Priestley's Experiments:
Oxygen Science Fair Projects and Experiments - Julian Rubin
Experiments with Oxygen - Bruce Mattson
Combustion, Phlogiston and Oxygen - PASCO
Who Discovered Oxygen?
When Did Antoine Lavoisier Discover Oxygen? - Fred Senese
Joseph Priestley: Discoverer of Oxygen - The Chemical Heritage Foundation
Joseph Priestley: The Discovery of Oxygen - Modern History Sourcebook
Oxygen - John H. Lienhard
Experiments with Oxygen - Bruce Mattson
Who Really Discovered Oxygen? - science.ca
Joseph Priestley - The Chemical Heritage Foundation
Joseph Priestley: The King of Serendipity - Useless Information
Antoine Lavoisier -Bruce Mattson
Antoine Lavoisier - Wikipedia
Antoine-Laurent Lavoisier - The Catholic Encyclopedia
Antoine-Laurent Lavoisier - The Chemical Heritage Foundation
Antoine Lavoisier - Eric Weisstein's World of Scientific Biography
Periodic Table of Elements: Oxygen - EnvironmentalChemistry.com
Oxygen - Wikipedia
(1) Joseph Priestley. Experiments and Observations on different kinds of air. 2nd ed. London: J. Johnson 1775 -1777. Vol. 1 – 3.