| Joseph Black | |
 Mezzotint engraving after Sir Henry Raeburn
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| Born | 16 April 1728 Bordeaux, France |
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| Died | 6 December 1799 Edinburgh |
| Nationality | Scottish |
| Fields | Medicine, physics, and chemistry |
| Doctoral students | James Watt |
| Known for | Latent heat, specific heat, and the discovery of carbon dioxide |
Joseph Black (16 April 1728 – 6 December 1799 [1]) was a Scottish physicist and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was a founder of thermochemistry who developed many pre-thermodynamics concepts, such as heat capacity, and was the mentor for James Watt. The chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after him.
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Black was born in Bordeaux, France, where his father, who was from Belfast, Ireland, was engaged in the wine trade. His mother was from Aberdeenshire, Scotland, and her family was also in the wine business. Joseph had twelve brothers and sisters.[2] He entered the University of Glasgow when he was eighteen years old, and four years later he went to Edinburgh to further his medical studies.
While at the University of Edinburgh, Black studied properties of carbon dioxide (CO2).[3]. One of his experiments involved placing a flame and mice into the carbon dioxide. Because both entities died, Black concluded that the air was not breathable. He named it 'fixed air' in 1754. In 1756 Black described how carbonates become more alkaline when they lose carbon dioxide, whereas the taking-up of carbon dioxide reconverts them. He was the first person to isolate carbon dioxide in a perfectly pure state. This was an important step in the history of chemistry as it helped people to realize that air was not an element, but rather was composed of many different things. Black's work also aided in discrediting the belief in a fiery principle called phlogiston.
In about 1750, Joseph Black developed the analytical balance based on a light-weight beam balanced on a wedge-shaped fulcrum. Each arm carried a pan on which the sample or standard weights was placed. It far exceeded the accuracy of any other balance of the time and became an important scientific instrument in most chemistry laboratories.[4].
In 1757, he was appointed Regius Professor of the Practice of Medicine at the University of Glasgow.
In 1761, wrote Ogg, Black deduced that the application of heat to ice does not cause its immediate liquefaction, rather the ice absorbed the heat without a rise in temperature.[5] Additionally, Black observed that the application of heat to boiling water does not result in immediate evaporation. From these observations, he concluded that the heat applied must have combined with the ice particles and boiling water and become latent. In espousing his theory of latent heat, said Ogg, the new subject of thermal science commenced.[6]
Black's theory of latent heat was one of his more-important scientific contributions, and one on which his scientific fame chiefly rests. He also showed that different substances have different specific heats. This all proved important not only in the development of abstract science but in the development of the steam engine.[7]
Black was a friend of James Watt, who first began his studies on steam power at Glasgow University in 1761. Black also was a member of the Poker Club and associated with David Hume, Adam Smith, and the literati of the Scottish Enlightenment. Black never married. He died in Edinburgh at the age of 71, and is buried there in Greyfriars Kirkyard.
