|Born||16 April 1728
|Died||6 December 1799 (aged 71)
|Alma mater||University of Glasgow
University of Edinburgh
|Known for||Latent heat, specific heat, and the discovery of carbon dioxide|
|Fields||Medicine, physics, and chemistry|
|Institutions||University of Edinburgh|
|Academic advisors||William Cullen|
|Notable students||James Edward Smith
Thomas Charles Hope
|Influenced||James Watt, Benjamin Rush|
Joseph Black FRSE FRCPE FPSG (16 April 1728 - 6 December 1799) was a Scottish physician and chemist, known for his discoveries of magnesium, 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.
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. He attended grammar school in Belfast from the age of 12 and entered the University of Glasgow in 1746 when he was eighteen years old, studying there for four years before spending another four at the University of Edinburgh, furthering his medical studies. During his studies he wrote a doctorate thesis on the treatment of kidney stones with the salt magnesium carbonate.
Like most eighteenth-century experimentalists, Black's conceptualisation of chemistry was based on five 'principles' of matter: Water, Salt, Earth, Fire and Metal. He added the principle of 'Air' when his experiments definitely confirmed the presence of carbon dioxide (which he called 'fixed air'). Black's research programme was guided by questions relating to how the foregoing principles combined with each other in various different forms and mixtures. He used the term 'affinity' to describe the force that held such combinations together. Throughout his career he used a variety of diagrams and formulas to teach his Edinburgh students how to manipulate affinity through different kinds of experimentation.
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 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.
In 1766, treading in the footsteps of his friend and former teacher at Glasgow, Black succeeded William Cullen as Professor of Medicine and Chemistry at the University of Edinburgh (Cullen had moved to Edinburgh in 1755). At this point he gave up research and devoted himself exclusively to teaching. In this he was very successful with audience attendance at his lectures increasing from year to year for more than thirty years. His lectures had a powerful effect in popularising chemistry and attendance at them even came to be a fashionable amusement.
Black was widely recognised as one of the most popular lecturers in the university. His chemistry course regularly attracted an exceptionally high number of students, with many attending two or three times. In addition to regularly introducing cutting-edge topics and meticulously selecting visually impressive experiments, Black employed a wide array of successful teaching tools that made chemistry accessible to his students (many of whom were as young as fourteen years old). His students came from across Britain, its colonies and Europe. Hundreds of them preserved his lectures in their notebooks and disseminated his ides after they left university.
On 17 November 1783 he was one of the founders of the Royal Society of Edinburgh. From 1788 to 1790 he was President of the Royal College of Physicians of Edinburgh. He was a member of the revision committee for the editions of the college's Pharmacopoeia Edinburgensis of 1774, 1783, and 1794. Black was appointed principal physician to George III in Scotland.
Another reason for his lack of research was his poor constitution. The least undue strain, whether physical or mental, produced spitting of blood and it was only through great care that he maintained unbroken, though feeble, health. However, from 1793 it visibly declined and he gradually withdrew more and more from his teaching duties. In 1795, Charles Hope was appointed his coadjutor in his professorship and in 1797 he lectured for the last time.
Black never married. He died peacefully at his home in Edinburgh in 1799 at the age of 71 and is buried in Greyfriars Kirkyard. The large monument lies in the sealed section to the south-west known as the Covenanter's Prison.
In 2011, scientific equipment believed to belong to Black was discovered during an archaeological dig at the University of Edinburgh.