From Wikipedia, the free encyclopedia

Joseph Black
Mezzotint engraving after Sir Henry Raeburn
Born	16 April 1728 Bordeaux, France
Died	6 December 1799 Edinburgh
Nationality	Scottish
Fields	Medicine, physics, and chemistry
Known for	Latent heat, specific heat, and the discovery of carbon dioxide
Influenced	James Watt

A precision analytical balance

Joseph Black FRSE FRCS (16 April 1728 – 6 December 1799^[1]) was a Scottish physician, 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), became involved in Black's works and conducted experiments on steam with Black. The chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after Black.

Aanalytical balance

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.^[2].

In 1757, he was appointed Regius Professor of the Practice of Medicine at the University of Glasgow.

Latent heat

In 1761 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.^[3] 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. The theory of latent heat marks the beginning of thermal science.^[4]

The world’s first ice-calorimeter, used in the winter of 1782-83, by Antoine Lavoisier and Pierre-Simon Laplace, to determine the heat evolved in various chemical changes, calculations which were based on Joseph Black’s prior discovery of latent heat.

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.^[5] 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, so saving a considerable amount of energy in reheating the water at every cycle of the engine.

Carbon dioxide

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.

See also

• Calorimetry
• Carbon dioxide
• Heat
• Pneumatic chemistry
• Thermochemistry
• Thermodynamics
• Timeline of hydrogen technologies

References

1. ^ Guerlac, Henry (1970–80). "Black, Joseph". Dictionary of Scientific Biography. 2. New York: Charles Scribner's Sons. pp. 173-183. ISBN 0684101149.  
2. ^ "Equal Arm Analytical Balances". http://history.nih.gov/exhibits/balances/index.html. Retrieved 2008-03-08.  
3. ^ Ogg, David (1965). Europe of the Ancien Regime: 1715-1783. Harper & Row.  
4. ^ Ogg, David (1965). Europe of the Ancien Regime: 1715-1783. Harper & Row. pp. 117 and 283.  
5. ^ Ogg, David (1965). Europe of the Ancien Regime: 1715-1783. Harper & Row. pp. 283.  

Further reading

External links

• Black's experiments on Alkaline Substances
• Joseph Black – Biographical information
• Joseph Black – Encyclopedia Britannica, 1911

From LoveToKnow 1911

(There is currently no text in this page)