This week’s question was asked by friends.
QUESTION: Who discovered oxygen and when?
ANSWER: The credit is generally given to Swedish scientist Carl Wilhelm Scheele in 1772. But there are a number of creditable claims by at least two others. Scheele termed his discovery “fire-air” because it supported combustion. He held off publishing his findings for five years, while in the meantime the English radical theologian and chemist, Joseph Priestly, discovered oxygen in 1774.
Priestly was fascinated by the bubbles (carbon dioxide) given off by beer vats in a nearby brewery in Leeds. He conducted experiments in a gun barrel, the test tube of his day. He would capture the gases emitted by heated substances. Before 1770, scientists knew only two pure gases, hydrogen and carbon dioxide.
Using a lens, Priestly focused sunlight, a rarity in England, onto a small pile of mercuric oxide. As the beam heated the red powder, liquid mercury bubbled out and a clear gas steamed upward from the powder. It was oxygen.
Priestly found that candles burned brightly, and mice in a jar did not keel over. He even tried some of the gas on himself, “I fancied that my breast felt particularly light and easy.” Priestly lost no time in publishing his results. But before the word got out, Priestly booked passage to Paris and was lavishly entertained by French aristocrat and chemist Antoine Lavoisier and his wife, Marie Ann.
Over much wine, Priestly blathered on about his oxygen discovery, something that Lavoisier was working on but had not noticed the stream of oxygen. As soon as Priestly left town, Lavoisier headed straight to his lab. Lavoisier married rich, he was 28 and she was 13, and owned half of the company, Ferme, that collected taxes for the crown. It was a royal shakedown as Lavoisier cleared as much as $5 million a year in today’s money.
Lavoisier poured his fortune into science. His team constructed a huge mobile lens that could burn diamonds with sunlight. The prevailing theory was that combustion was supported by a substance called phlogiston. After numerous experiments, Lavoisier proved that oxygen explained the chemistry of burning and that burning always seemed to involve oxygen combining with a substance and releasing heat and light. For example, wood and coal combined with oxygen to form carbon dioxide, which then floated away.
In September 1775, Lavoisier made claim to this new element, which he called oxygen, at a scientific meeting in Paris, just one year after blabbermouth Priestly tipped him off. Over in England, Priestly fumed.
Who gets credit for discovering oxygen? Scheele and Priestly both isolated and collected oxygen, but neither man understood what he found. Lavoisier went steps further. He developed a fundamental law of chemistry, the law of conservation of mass. In any reaction, the amount of stuff before a reaction must equal the amount of stuff after the reaction.
Lavoisier proposed that all substances were either elements or combinations of elements, the most fundamental idea in chemistry. His book, Elementary Treatise on Chemistry, published in 1789, is considered the very first chemistry textbook. Unfortunately for poor Antoine, 1789 was the start of the bloody French Revolution.
The new mob in Paris abolished Lavoisier’s money-making tax collecting scheme. Years earlier, he was known for installing a hated wall around Paris and collecting tolls at guarded gates. A warrant was issued for his arrest in 1793. Lavoisier hid in the Louvre for a few days before turning himself in on Christmas Eve.
Lavoisier, age 50, and 27 others of their tax-raising company, Ferme, were put on trial at 10 a.m. on May 7, 1794. The charges were fixing interest rates, watering down tobacco, and embezzling $5 billion dollars (today’s money). They were found guilty in the early afternoon and were ox-carted to the guillotine at 5 p.m. Lavoisier was fourth in line and all 28 had lost their heads in a half hour.
Eighteen months after his death, Lavoisier was exonerated by the French government. His belongings were delivered to his widow, with an attached note, “To the widow of Lavoisier, who was falsely convicted.”
Larry Scheckel is a retired Tomah High School physics teacher. Send questions and comments to email@example.com.
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