| Joseph Black | |
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Mezzotint engraving by James Heath after Sir Henry Raeburn
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| Born | 16 April 1728 Bordeaux, France |
| Died | 6 December 1799 (71 years old.) Edinburgh |
| Nationality | Scottish |
| Fields | Medicine, physics, and chemistry |
| Known for | Latent heat, specific heat, and the discovery of carbon dioxide |
| Influenced | James Watt |
Joseph Black FRSE FRCPE FPSG (16 April 1728 – 6 December 1799[1]) was a Scottish physician and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was professor of Medicine at University of Glasgow (where he also served as lecturer in Chemistry). James Watt, who was appointed as philosophical instrument maker at the same university (1756). Watt consulted with Black on experiments with his steam engine. Watt and Black also collaborated in project to manufacture sodium hydroxide; however, Black was not known to have any business interest in the process, which did not enjoy commercial success.[2] The chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after Black.
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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.[3] 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.
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 Black deduced that the application of heat to ice at its melting point does not cause a rise in temperature of the ice/water mixture, but rather an increase in the amount of water in the mixture. Additionally, Black observed that the application of heat to boiling water does not result in a rise in temperature of a water/steam mixture, but rather an increase in the amount of steam. From these observations, he concluded that the heat applied must have combined with the ice particles and boiling water and become latent. The theory of latent heat marks the beginning of thermodynamics.[5]
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.[6] The latent heat of water is large compared with many other liquids, so giving impetus to James Watt's successful attempts to improve the efficiency of the steam engine invented by Thomas Newcomen. Watt added a separate condenser, and kept the cylinder at the temperature of steam (by enclosing it in a steam-filled jacket) so saving a considerable amount of energy in avoiding the reheating of the cylinder at every cycle of the engine.
Black also explored the properties of a gas produced in various reactions. He found that limestone (calcium carbonate) could be heated or treated with acids to yield a gas he called "fixed air." He observed that the fixed air was denser than air and did not support either flame or animal life. Black also found that when bubbled through an aqueous solution of lime (calcium hydroxide), it would precipitate calcium carbonate. He used this phenomenon to illustrate that carbon dioxide is produced by animal respiration and microbial fermentation.
In 1757 or 1758 Black became a friend of James Watt, who first began his studies on steam power at Glasgow University in 1761. He provided significant financing and other support for Watt's early research on the steam engine. 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. In 2011 scientific equipment believed to belong to Black was discovered during an archeological dig at the University of Edinburgh.[7]