Joseph Black

Joseph Black

Black's tomb in Edinburgh

Joseph Black (born April 16, 1728 in Bordeaux , France , † December 6, 1799 in Edinburgh ) was a Scottish physicist and chemist . He is the discoverer of carbon dioxide , is often counted among the discoverers of the element magnesium and introduced latent heat .

Life

Joseph Black was the son of an Irish-born wine merchant, John Black, who lived in Scotland and later in Bordeaux. The large family had contact with Montesquieu in France . At the age of 12, Black was sent to his homeland in Belfast, at 18 (1746) he attended the University of Glasgow and attended chemical lectures by the rhetorical William Cullen . In 1751 he moved to the University of Edinburgh to Robert Whytt .

His doctoral thesis, De humore acido a cibis orto et Magnesia alba , made in 1754, dealt with studies on magnesium oxide and magnesium carbonate . In 1755 his treatise Experiments upon Magnesia alba and other Alcaline Substances appeared . Because of this work, Black succeeded William Cullen in Glasgow. He recognized the difference between calcium carbonate and magnesium carbonate and was the first to systematically study magnesium compounds, the prototypes of which were then known as Epsom Salt and Magnesia Alba and were used in medicine. That is why he is often counted among the discoverers of magnesium, even if it was only later isolated by Humphry Davy using electrolysis. A few years after Black, Andreas Sigismund Marggraf independently also found magnesium in minerals of the serpentine group and Black cites further examples of its occurrence in Lectures on the elements of chemistry . Black's work of 1755 was particularly important for the experiments described below for the detection of carbon dioxide.

Background of Black's work was a secret recipe on the relief of gallstones by Joanna Stephens . Stephen Hales, who wanted to make the recipe publicly available through a well-rewarded award ceremony, also sponsored the research on the dissolution of gallstones by lime water at Professors Whytt, Alston.

Around 1762 Black was studying latent heat; H. the temperature constancy of a thermometer at the boiling point and freezing point of water. Black's knowledge of latent heat also influenced the development of the first steam engine. James Watt , who introduced decisive improvements to the steam engine, attended lectures at Black.

Like his teacher Cullen, he was one of those who used symbolic diagrams for reactions early on.

In 1766 Black was appointed professor of chemistry at Edinburgh University.

Since January 30, 1783 he was an honorary member of the Russian Academy of Sciences . In the same year he was elected a Fellow of the Royal Society of Edinburgh . On May 15, 1789 Black became a corresponding member, associé étranger of the French Académie des sciences . The moon crater Black and the asteroid (5883) Josephblack are named after him.

His students included Jędrzej Śniadecki , Benjamin Rush , Thomas Charles Hope , William Irvine, and Richard Lubbock . His immediate successor to his professorship was John Robison , followed by Irvine and Hope.

Scientific work

carbon dioxide

Black is considered to be a pioneer for the creation of quantitative chemistry by Antoine Laurent de Lavoisier . At that time there was no knowledge of atoms, molecules, molecular mass or the exact causes of changes in mass during the transformation of substances. Black was not yet able to detect the elements carbon and oxygen in the fixed air (carbon dioxide) - Lavoisier later did that - but he determined the mass and the types of transformation of the fixed air and thus made an important contribution to the later elucidation of this substance .

Black heated 7.2 grams of magnesium carbonate (Magnesia) and determined the weight of the residue to be about 3.1 grams. Black suspected that air (phlogiston) would escape during the combustion process. He dissolved the magnesium carbonate, which had been converted to magnesium oxide, in a little sulfuric acid (vitrolic acid), mixed the solution with sodium carbonate solution and again obtained an insoluble solid. After careful washing and drying, he determined the weight of this fabric to be 6.6 g. Gas (carbon dioxide) was again evolved under the influence of acids. With this conversion, he reintroduced the fixed air into the burnt magnesia (magnesium oxide) produced during the combustion. During the feeding process, however, no development of air was visible, so that the fixed air presumably came from the carbonate solution. This thought process was not easy to understand in the light of the phlogiston theory , since the phlogiston could only escape when gas was generated or burned. Black then examined the changes in mass when the acid was added to the sodium carbonate solution. He later discovered that magnesium oxide (burnt magnesia) needed more acid to neutralize than magnesium carbonate, and he also realized that fixed air is also present in ordinary air.

Black recognized in his work De humore acido a cibis orto et Magnesia alba in 1755 the difference between lime ( calcium carbonate ) and magnesia alba ( magnesium carbonate ), which were often confused at that time. He understood Magnesia alba as the carbonate of a new element. This is why Joseph Black is often cited as the discoverer of magnesium , although he was never able to represent pure magnesium.

Amount of heat

Black also studied the change in temperature of water with a thermometer. When heat was applied to a water vessel, the mercury scale of the thermometer expanded, while ice did not show any temperature change for a long time when heat was applied. Even with the formation of water vapor, the temperature of the thermometer did not change. Black concluded that even though the temperature did not change, heat would still be added as it boiled and melted. Black realized that a distinction had to be made between the intensity (temperature) and the amount of heat (quantity). Black also found that different fabrics could absorb different amounts of heat.

Black was an discoverer of heat capacity and specific heat through his theory of latent heat .

Publications

• Lectures on the elements of chemistry in 2 volumes, edited by Robinson based on Black's handwriting, Edinburgh 1803 (German by Crell, Hamburg 1804–1805 in 4 volumes)

literature

• Douglas McKie , NH de. V. Heathcote: The Discovery of Specific and Latent Heat, 1935
• Georg Lockemann: History of Chemistry . Volume 1, Walter de Gruyter Verlag, Berlin 1955, pp. 102-104.
• Douglas McKie: Thomas Cochrane's Notes from Doctor Black's Lectures on Chemistry 1767–1768, 1966
• Henry Guerlac : Black, Joseph . In: Dictionary of Scientific Biography . 2nd edition, Charles Scribner's Sons, New York 1970, pp. 173-183.
• Max Speter: Black . In: The Book of Great Chemists . Verlag Chemie, Weinheim 1974, ISBN 3-527-25021-2 .
• Hans Joachim Störig : Brief World History of the Sciences 1 . Fischer Verlag, Frankfurt a. M., 1980, ISBN 3596-26398-0 , p. 391.
• Robert GW Anderson , JG Fyffe (Eds.): Joseph Black. A Bibliography . Science Museum, London 1992.
• Robert GW Anderson, Jean Jones (Eds.): The Correspondence of Joseph Black . Ashgate, Farnham 2012.

Web links

• Joseph Black , entry in the Encyclopædia Britannica 1911 (English)

Individual evidence

1. ^ Mary Weeks: Discovery of the elements . 1956, p. 523.
2. ^ Edward L. Keyes: The Joanna Stephens Medicines for the Stone. In: Bulletin of the New York Academy of Medicine 18, 1942, pp. 835-840 PMC 1933931 (free full text); Lester Blum: An Eighteenth Century Health Care Provider and Medical Entrepreneur . In: Bulletin of the New York Academie of Medicine 60, 1984, pp. 944-947 PMC 1911790 (free full text); David Hartley: Ad virum clarissimum Ric. Mead, MD epistola, varias lithontripticum Joannæ Stephens, exhibendi methodos indicans. 1751.
3. ^ MP Crosland: The use of diagrams as chemical 'equations' in the lectures of William Cullen and Joseph Black . In: Annals of Science , Volume 15, 1959, pp. 75-90.
4. ↑ Chemiedidaktik Universität Oldenburg by Malcolm Hadfiel (PDF file; 73 kB).
5. ^ Foreign members of the Russian Academy of Sciences since 1724. Joseph Black. Russian Academy of Sciences, accessed August 2, 2015 . 
6. ^ Biographical Index: Former RSE Fellows 1783–2002. Royal Society of Edinburgh, accessed October 9, 2019 .