Everything about Carl Wilhelm Scheele totally explained
Carl Wilhelm Scheele (
December 9,
1742 –
May 21,
1786) was a
German-
Swedish pharmaceutical chemist, born in
Stralsund, Western
Pomerania,
Germany (at the time under Swedish rule). He was the discoverer of many chemical substances, most notably discovering
oxygen (although
Joseph Priestley published his findings first),
molybdenum and
chlorine before
Humphry Davy.
Biography
Instead of becoming a carpenter like his father, Scheele decided to become a pharmacist. His career as a
pharmacist began with his apprenticeship at an apothecary in
Gothenburg when he was only fourteen years old. He retained this position for eight years before becoming an apothecary's clerk in
Malmö. Then Scheele worked as a
pharmacist in
Stockholm, from 1770-1775 in
Uppsala, and later in
Köping. In 1776, he was able to establish his own pharmacy, which he'd purchased from the previous owner's widow. The two married, but Scheele passed away 48 hours later.
Scientific career
Despite his lack of a thorough education, he clearly had an instinctive flair for
experimentation. Scheele's limited formal instruction makes his successes all the more surprising. The schooling which Scheele did have was private and it was through this education that he exhibited an inclination to study the art of the
pharmacist. He put substantial effort into learning as much as he could in
science, even staying up late at night reading different chemical books.
Unlike scientists such as
Antoine Lavoisier and
Isaac Newton who were more widely recognized, Scheele had a humble position in a small town, and preferred that to the grandeur of an extravagant house, yet he was still able to make significant scientific discoveries. Scheele turned down high-paying offers by prestigious European academies.
Frederick II offered him a
Berlin position, and the English government offered him a generous salary for his work, but Scheele remained at his pharmacy to serve his faithful customers.
Scheele made many discoveries in
chemistry before others who are generally given the credit, and his numerous discoveries have yet to be surpassed. One of Scheele's most famous discoveries was
oxygen produced as a by-product in a number of experiments in which he heated chemicals during 1771-1772. Scheele, though, didn't name or define oxygen; that job would fall to
Antoine Lavoisier, the second to quantitatively isolate the gas, (August 1774), who published a paper with the new name in 1775.
Scheele described the discovery of
oxygen and
nitrogen (1772-1773), in his only book,
Chemische Abhandlung von der Luft und dem Feuer (
Chemical Treatise on Air and Fire) in 1777, losing some fame to
Joseph Priestley, who independently discovered oxygen in 1774. In his book, he also distinguished
heat transfer by
thermal radiation from that by
convection or
conduction. Like many other chemists of his time, Scheele often worked under difficult and even dangerous conditions. Also, he'd a habit of tasting chemicals that he found. It appears that this was the cause of his premature death at the age of 43; his death symptoms resemble
mercury poisoning. (Scheele also discovered an element called Molybdenum (Mo), which is now number 42 on the Periodic Table of the Elements. He discovered it in Köping, Sweden.)
The possibly apocryphal story is told that Scheele was to be ennobled by
Gustavus III for his discoveries, but that the honor was mistakenly conferred on an obscure soldier of the same name (Fuller's Thesaurus of Anecdotes, 1116).
Existing theories before Scheele
By the time he was a teenager, Scheele had learned the dominant theory on gases in the 1770s, the
phlogiston theory.
Phlogiston, classified as "matter of fire" stated that any material that was able to burn would release
phlogiston during combustion, and stops when all the
phlogiston had been released. When Scheele discovered
oxygen he called it "fire air" because it supported combustion, but he explained oxygen using phlogistical terms because he didn't believe that his discovery disproved the
phlogiston theory. Before Scheele made his discovery of
oxygen, he studied air. Air was thought to be an element that made up the environment in which chemical reactions took place but didn't interfere with the reactions. Scheele's investigation of air enabled him to conclude that air was a mixture of "fire air" and "foul air;" in other words, a mixture of two gases. He performed numerous experiments in which he burned substances such as saltpeter (
potassium nitrate),
manganese dioxide, heavy metal nitrates,
silver carbonate and
mercuric oxide. In all of these experiments, he isolated gas with the same properties; his "fire air," which he believed combined with
phlogiston to be released during heat-releasing reactions. However, his first publication,
A Chemical Treatise on Air and Fire, wasn't released until 1777 at which time both
Joseph Priestley and
Lavoisier had already published their experimental data and conclusions concerning
oxygen and the
phlogiston theory.
Debunking the theory of phlogiston
Historians of science no longer question the role of Carl Scheele in the overturning of the
phlogiston theory. It is generally accepted that he was the first to discover oxygen, among a number of prominent scientists (namely his adversaries
Antoine Lavoisier,
Joseph Black, and
Joseph Priestley). In fact, it was determined that Scheele made the discovery three years prior to
Joseph Priestley and at least several before
Lavoisier.
Joseph Priestley relied heavily on Scheele's work, perhaps so much so that he wouldn't have made the discovery of
oxygen on his own. Correspondence between
Lavoisier and Scheele indicate that Scheele achieved interesting results without the advanced laboratory equipment that
Lavoisier was accustomed to. Through the studies of
Lavoisier,
Joseph Priestley, Scheele, and others,
chemistry was made a standardized field with consistent procedures. Although Scheele was unable to grasp the significance of his discovery of
oxygen, his work was essential for the invalidation of the long-held theory of
phlogiston.
Scheele's study of the gas not yet named
oxygen was sparked by a complaint by
Torbern Olof Bergman.
Bergman informed Scheele that the saltpeter he purchased from Scheele's employer produced red vapors when it came into contact with acid. Scheele's quick explanation for the vapors led
Bergman to suggest that Scheele analyze the properties of
manganese dioxide. It was through his studies with
manganese dioxide that Scheele developed his concept of "fire air." He ultimately obtained
oxygen by heating
mercuric oxide,
silver carbonate,
magnesium nitrate, and
saltpeter. Scheele wrote about his findings to
Lavoisier who was able to grasp the significance of the results.
In addition to his joint recognition for the discovery of oxygen, Scheele is argued to have been the first to discover other chemical elements such as
barium (1774),
manganese (1774),
molybdenum (1778), and
tungsten (1781), as well as several chemical compounds, including
citric acid,
lactic acid,
glycerol,
hydrogen cyanide (also known, in aqueous solution, as prussic acid),
hydrogen fluoride, and
hydrogen sulfide. In addition, he discovered a process similar to
pasteurization, along with a means of mass-producing
phosphorus (1769), leading Sweden to become one of the world's leading producers of matches.
Scheele made one other very important scientific discovery in 1774, arguably more revolutionary than his isolation of
oxygen. He identified
lime,
silica, and
iron, in a specimen of
pyrolusite given to him by his friend,
Johann Gottlieb Gahn, but couldn't identify an additional component. When he treated the
pyrolusite with
hydrochloric acid over a warm sand bath, a yellow-green gas with a strong odor was produced. He found that the gas sank to the bottom of an open bottle and was denser than ordinary air. He also noted that the gas wasn't soluble in water. It turned corks a yellow color and removed all color from wet, blue litmus paper and some flowers. He called this gas with bleaching abilities, "dephlogisticated marine acid" (dephlogisticated
hydrochloric acid) Eventually,
Sir Humphrey Davy named the gas
chlorine.
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