This was theoretically impossible. The ever-curious Priestley wanted to know how it could happen. So in August , he obtained a sample of mercury calx and used a burning lens to heat it with sunlight. Two months later, he shared his findings over dinner with Lavoisier in Paris. Paying close attention to the weights of his experimental ingredients, Lavoisier noticed that metals gain weight as they rust.
Even though theory said phlogiston was leaving the metal, the resulting calx was heavier than the metal from which it formed. Puzzled, Lavoisier began a series of experiments that revealed the source of this weight gain: Air, or some part of air, was absorbed into the metal as it rusted.
For two years, Lavoisier had searched in vain for the identity of this mystery gas. Lavoisier hurried to the local apothecary to buy his own sample of mercury calx. Across the English Channel, Lavoisier was performing his own experiments on mercury calx, discovering the same properties Priestley had observed. But in a move that is still earning him criticism more than two centuries later, Lavoisier failed to acknowledge his debt to Priestley.
While it was Priestley who isolated this new gas, it was Lavoisier who grasped its profound implications. Over the next 15 years, he would make oxygen the foundation of a whole new chemistry, showing that it was a key ingredient in both air and water, and that fire was not an element, as the ancients believed, but a process of combining with oxygen.
Centuries later, scholars continue to debate who deserves credit for discovering oxygen. Or Lavoisier, who understood what the new gas meant? While Priestley never accepted the revolutionary importance of his own discovery, he did make a critical finding about the importance of oxygen to life on earth.
It was a fundamental contribution to environmental science. As his scientific activity waned, Priestley took an ever greater interest in politics, offering vocal support for the American cause in the Revolutionary War and, a decade later, for the French rebels who overthrew King Louis the XVI.
He fled to America and spent the last ten years of his life in Pennsylvania. By doing so, Johnson notes, Priestley set a precedent for the many other intellectual exiles who would follow.
He settled in Northumberland, Pennsylvania although his scientific work never recovered from his forced departure. But the descriptions of his experiments with oxygen will always remain a high point in the history of respiratory physiology.
Keywords: Warrington Academy; dephlogisticated air; discovery of gases; forced emigration; liberal views. Abstract Joseph Priestley — was the first person to report the discovery of oxygen and describe some of its extraordinary properties.
Publication types Biography Historical Article Portrait. Substances Oxygen. Find a chemistry community of interest and connect on a local and global level. Technical Divisions Collaborate with scientists in your field of chemistry and stay current in your area of specialization.
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An Englishman by birth, Priestley was deeply involved in politics and religion, as well as science. When his vocal support for the American and French revolutions made remaining in his homeland dangerous, Priestley left England in and continued his work in America until his death.
Some 2, years ago, the ancient Greeks identified air — along with earth, fire and water — as one of the four elemental components of creation. That notion may seem charmingly primitive now. But it made excellent sense at the time, and there was so little reason to dispute it that the idea persisted until the late 18th century.
It might have endured even longer had it not been for a free-thinking English chemist and maverick theologian named Joseph Priestley. Priestley was hugely productive in research and widely notorious in philosophy. He invented carbonated water and the rubber eraser, identified a dozen key chemical compounds, and wrote an important early paper about electricity.
His unorthodox religious writings and his support for the American and French revolutions so enraged his countrymen that he was forced to flee England in He settled in Pennsylvania, where he continued his research until his death. The world recalls Priestley best as the man who discovered oxygen, the active ingredient in our planet's atmosphere.
In the process, he helped dethrone an idea that dominated science for 23 uninterrupted centuries: Few concepts "have laid firmer hold upon the mind," he wrote, than that air "is a simple elementary substance, indestructible and unalterable.
In a series of experiments culminating in , Priestley found that "air is not an elementary substance, but a composition," or mixture, of gases.
Among them was the colorless and highly reactive gas he called "dephlogisticated air," to which the great French chemist Antoine Lavoisier would soon give the name "oxygen. It is hard to overstate the importance of Priestley's revelation. Scientists now recognize 92 naturally occurring elements-including nitrogen and oxygen, the main components of air. They comprise 78 and 21 percent of the atmosphere, respectively. In the midth century, the concept of an element was still evolving.
Researchers had distinguished no more than two dozen or so elements, depending on who was doing the counting. It wasn't clear how air fit into that system. Nobody knew what it was, and researchers kept finding that it could be converted into such a variety of forms that they routinely spoke of different "airs.
The principal method for altering the nature of air, early chemists learned, was to heat or burn some compound in it. The second half of the s witnessed an explosion of interest in such gases. The steam engine was in the process of transforming civilization, and scientists of all types were fascinated with combustion and the role of air in it.
British chemists were especially prolific. In , Joseph Black identified what he called "fixed air" now known to be carbon dioxide because it could be returned, or fixed, into the sort of solids from which it was produced. In , a wealthy eccentric named Henry Cavendish produced the highly flammable substance Lavoisier would name hydrogen, from the Greek words for "water maker. Finally in , Daniel Rutherford found that when he burned material in a bell jar, then absorbed all the "fixed" air by soaking it up with a substance called potash, a gas remained.
Rutherford dubbed it "noxious air" because it asphyxiated mice placed in it. Today, we call it nitrogen. But none of those revelations alone tells the whole story. The next major discovery would come from a man whose early life gave no indication that he would become one of the greatest experimental chemists in history.
In , Priestley was offered a ministry in Leeds, Englane, located near a brewery. He found a way to produce artificially what occurred naturally in beer and champagne: water containing the effervescence of carbon dioxide. The method earned the Royal Society's coveted Copley Prize and was the precursor of the modern soft-drink industry. Joseph Priestley was born in Yorkshire, the eldest son of a maker of wool cloth. His mother died after bearing six children in six years. Young Joseph was sent to live with his aunt, Sarah Priestley Keighley, until the age of She often entertained Presbyterian clergy at her home, and Joseph gradually came to prefer their doctrines to the grimmer Calvinism of his father.
Before long, he was encouraged to study for the ministry. And study, as it turned out, was something Joseph Priestley did very well. Aside from what he learned in the local schools, he taught himself Latin, Greek, French, Italian, German and a smattering of Middle Eastern languages, along with mathematics and philosophy.
This preparation would have been ideal for study at Oxford or Cambridge, but as a Dissenter someone who was not a member of the Church of England Priestley was barred from England's great universities.
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