Joseph Black

Joseph Black FRSE FRCPE FPSG (16 April 1728 – 6 December 1799) was a Scottish physician and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was Professor of Anatomy and Chemistry at the University of Glasgow for 10 years from 1756, and then Professor of Medicine and Chemistry at the University of Edinburgh from 1766, teaching and lecturing there for more than 30 years.The chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after Black.In about 1750, while still a student, 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.In 1757, Black was appointed Regius Professor of the Practice of Medicine at the University of Glasgow.In 1761 he 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. 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.The theory ultimately proved important not only in the development of abstract science but in the development of the steam engine. The latent heat of water is large compared with many other liquids, so giving impetus to James Watt's attempts to improve the efficiency of the steam engine invented by Thomas Newcomen. Black and Watt became friends after meeting around 1757 while both were at Glasgow. Black provided significant financing and other support for Watt's early research in steam power.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.Black never married. He died peacefully at his home in Edinburgh in 1799 at the age of 71 and is buried in Greyfriars Kirkyard.In 2011 scientific equipment believed to belong to Black was discovered during an archaeological dig at the University of Edinburgh.