Carl Wilhelm Scheele

Carl Wilhelm Scheele
Carl Scheele
Born	9 December 1742 (1742-12-09) Stralsund, Swedish Pomerania, today Germany
Died	21 May 1786 (1786-05-22) (aged 43) Köping, Sweden
Nationality	German-Swedish
Fields	Chemistry
Known for	Discovered oxygen (independently), molybdenum, tungsten and chlorine

Carl Wilhelm Scheele (9 December 1742 – 21 May 1786) was a German-Swedish pharmaceutical chemist. Isaac Asimov called him "hard-luck Scheele" because he made a number of chemical discoveries before others who are generally given the credit. For example, Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hydrogen, and chlorine before Humphry Davy, among others.

Scheele was born in Stralsund, Swedish Pomerania. Scheele's father Joachim Christian Scheele, was a merchant of a respected German family. At fourteen, he was sent as an apprentice pharmacist in Gothenburg with Martin Andreas Bauch. 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.

Scheele preferred speaking German his whole life, and German was commonly spoken among Swedish pharmacists.

Existing theories before Scheele

By the time he was a teenager, Scheele had learned the dominant theory of gases in the 1770s, the phlogiston theory. Phlogiston, classified as "matter of fire", was supposed to be released from any burning material, and when it was exhausted, combustion would stop. When Scheele discovered oxygen he called it "fire air" because it supported combustion, but he explained oxygen using phlogistical terms because he did not 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 did not 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, Chemische Abhandlung von der Luft und dem Feuer, was delivered to the printer Swederus in 1775, but not published until 1777, at which time both Joseph Priestley and Lavoisier had already published their experimental data and conclusions concerning oxygen and the phlogiston theory. The first English edition, Chemical Observation and Experiments on Air and Fire was published in 1780, with an introduction "Chemical Treatise on Air and Fire"

Disproving the theory of phlogiston

Joseph Priestley .

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 esteemed colleagues Antoine Lavoisier, Joseph Black, and Joseph Priestley). In fact, it was determined that Scheele made the discovery three years prior to Priestley and at least several before Lavoisier. Joseph Priestley relied heavily on Scheele's work, perhaps so much so that he would not 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 prompted by a complaint by Torbern Olof Bergman. Bergman informed Scheele that the saltpeter he had 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 of manganese dioxide that Scheele developed his concept of "fire air." He ultimately obtained oxygen by heating mercuric oxide, silver carbonate, magnesium nitrate, and other nitrate salts. Scheele wrote about his findings to Lavoisier who was able to see the significance of the results.

Pyrolusite or MnO₂.

New elements and compounds

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.

Chlorine gas.

Statue of Scheele in Köping.

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 (impure manganese dioxide) given to him by his friend, Johann Gottlieb Gahn, but could not identify an additional component (this was the manganese, which Scheele recognized was present, but could not isolate). 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 was not 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 muriatic acid" (dephlogisticated hydrochloric acid). Eventually, Sir Humphry Davy named the gas chlorine.

Death

While Scheele's experiments generated substances which have long since been found to be hazardous, the compounds and elements he used to start his experiments were dangerous to begin with, especially heavy metals. Scheele had a bad habit of sniffing and tasting any new substances he discovered. Cumulative exposure to mercury, lead, their compounds, fluoric acid, and other substances took their toll on Scheele, who died on 21 May 1786 at his home in Köping. He married the widow Pohl two days before he died so that he could pass on his possessions and his pharmacy to someone.

See also

• Scheelite
• Scheele's Green
• Pharmacist
• Pharmacy
• Pneumatic chemistry
• List of independent discoveries

References

• Abbott, David. (1983). Biographical Dictionary of Scientists: Chemists. New York: Peter Bedrick Books. pp. 126–127. ISBN 0-911745-81-5. 
• Bell, Madison S. (2005). Lavoisier in the Year One. New York: W.W. Norton & Company, Inc. ISBN 0-393-05155-2. 
• Cardwell, D.S.L. (1971). From Watt to Clausius: The Rise of Thermodynamics in the Early Industrial Age. Heinemann: London. pp. 60–61. ISBN 0-435-54150-1. 
• Dobbin, L. (trans.) (1931). Collected Papers of Carl Wilhelm Scheele. G. Bell & Sons, London. 
• Farber, Eduard ed. (1961). Great Chemists. New York: Interscience Publishers. pp. 255–261. 
• Greenberg, Arthur. (2000). A Chemical History Tour: Picturing Chemistry from Alchemy to Modern Molecular Science. Hoboken: John Wiley & Sons, Inc. pp. 135–137. ISBN 0-471-35408-2. 
• Greenberg, Arthur. (2003). The Art of Chemistry: Myths, Medicines and Materials. Hoboken: John Wiley & Sons, Inc. pp. 161–166. ISBN 0-471-07180-3. 
• Schofield, Robert E (2004). The Enlightened Joseph Priestley: A Study of His Life and Work from 1773-1804. Pennsylvania: The Pennsylvania State University Press. ISBN 0-271-02459-3. 
• Shectman (2003). Groundbreaking Scientific Experiments, Inventions, and Discoveries of the 18th Century. Connecticut: Greenwood Press. ISBN 0-313-32015-2. 
• Sootin, Harry (1960). 12 Pioneers of Science. New York: Vanguard Press. 

External links

• Excerpts from the Chemical Treatise on Air and Fire
•  Chisholm, Hugh, ed. (1911). "Scheele, Karl Wilhelm". Encyclopædia Britannica (11th ed.). Cambridge University Press. 
•  "Scheele, Carl Wilhelm". The Nuttall Encyclopædia. 1907. 
•  "Sketch of Karl Wilhelm Scheele". Popular Science Monthly 31: 839–843. October 1887. 
•  "The Scheele Monument at Stockholm". Popular Science Monthly 42: 685–688. March 1893.