Summary

Joseph Black (16 April 1728 - 6 December 1799) was a Scottish chemist and physician, known for his discovery of specific heat, latent heat, magnesium and carbon dioxide. He was Professor of Anatomy and Chemistry at the University of Glasgow from 1756, and then Professor of Medicine and Chemistry at the University of Edinburgh from 1766.

Black was born in Bordeaux, France, where his father, originally from Belfast, Ireland, was a wine merchant. His mother came from Aberdeenshire, Scotland, and her family had the same occupation. Joseph had 12 brothers and sisters. He was educated at Belfast Grammar School from the age of 12 and at 18 he entered Glasgow University, studying there for four years before spending a further four years at Edinburgh University, continuing his medical studies there. During his studies, Black wrote a doctoral thesis on the treatment of kidney stones with magnesium carbonate.

The foundations of its chemistry

As was the case with most 18th-century experimenters, Joseph Black's conception of chemistry was based on the five 'roots' of matter: water, earth, fire, salts and metals. To these he added 'air' when his experiments confirmed the presence of carbon dioxide (which he called 'fixed air'). Black's research was driven by questions about how these rhizomes combined with each other in a variety of forms and mixtures. The force that held them together in such combinations he called affinity. Throughout his career he applied a variety of diagrams and formulas to teach his students how to manipulate chemical affinity through different experiments.

The analytical balance

Around 1750, while still a student, Black developed the precision laboratory balance or "analytical balance", based on a light rod balanced on a wedge-shaped sub-millimeter. Each arm of the balance carried a tray on which he placed the sample or weights (balances). This arrangement exceeded the accuracy of any other balance of the time and became an important scientific tool in most chemistry laboratories.

The latent heat

In 1757 Black was appointed "professor of medicine and therapeutics in the Regius chair of the University of Glasgow. In 1761 he realised that adding heat to melting ice does not cause an increase in the temperature of the ice-water mixture, only more melting of the ice. Furthermore, Black observed that adding heat to boiling water does not cause an increase in the temperature of the water-vapor mixture, but an increase in the amount of steam. From these observations he concluded that the heat added must have been absorbed by the particles of the ice and boiling water respectively and became 'latent'.

This theory of latent heat marked the beginning of scientific thermodynamics. and is one of the Scottish scientist's most important contributions, on which his scientific reputation is based. Black also proved that different substances have different specific heats.

This theory eventually proved to be important not only for the development of theoretical science, but also for the development of the steam engine. The latent heat of water is high compared to that of many other liquids, which influenced James Watt's efforts to improve the efficiency of the steam engine invented by Thomas Newkamen. Black and Watt became friends after meeting around 1757, when both were working at the University of Glasgow. Black provided considerable financial and other support for Watt's early investigations into the power of steam.

The discovery of carbon dioxide

Black studied the properties of a gas that he found was released in various reactions. He discovered that limestone (calcium carbonate), when heated or exposed to acids, gave off a gas that he called 'fixed air'. He found that the 'fixed air' was denser than atmospheric air and did not support combustion (flame) or animal respiration. Black also found that, by passing this gas through lime water (i.e. an aqueous solution of calcium hydroxide), it caused calcium carbonate to precipitate. He used this phenomenon to observe that the gas was produced by respiration and microbial fermentation.

In 1766, following the example of his friend and former professor in Glasgow, Black succeeded William Cullen as professor of medicine and chemistry at the University of Edinburgh (Cullen had settled in Edinburgh in 1755). From then on, Black left research and devoted himself exclusively to teaching. At this he was very good, with attendance at his lectures rising from year to year for more than thirty years. His lectures exerted a powerful influence on the popularization of chemistry, and attending them came to be a popular outlet.

Black was widely recognized as one of the most popular speakers at the university. His chemistry course regularly attracted an extremely large number of students. In addition to his regular introduction to cutting-edge topics and his careful selection of visually striking experiments, Black used a variety of successful teaching aids that made chemistry accessible to his students (many of whom were as young as 14 years old). His students came from all over Britain, its colonies, and continental Europe. Hundreds of them preserved his traditions in their notebooks and spread his ideas after graduation.

On 17 November 1783 Black participated in the founding of the Royal Society of Edinburgh. From 1788 to 1790 he was president of the Royal College of Physicians of Edinburgh. He was also a member of the committee revising the 'Pharmacopoeia Edinburgensis' for the 1774, 1783 and 1794 editions, and was appointed chief physician to King George III for the periods when the latter visited Scotland.

An important reason for Black's abandonment of scientific research was his weak constitution. The least extra strain, either physical or mental, caused him to haemorrhage, and only with great care could he maintain his health. However, from 1793 onwards he became visibly weakened and gradually withdrew from his teaching duties. In 1795 Charles Hope was appointed assistant to his chair, and in 1797 Black delivered his last lesson.

Black was a member of the Poker Club, where many people who pioneered the so-called "Scottish Enlightenment" met and exchanged views. He associated with David Hume, Adam Smith and others, including geology pioneer James Hutton.

Joseph Black never married. He died peacefully at his home in Edinburgh at the age of 71 and was buried in the city's Greyfriars Kirkyard Cemetery. His relatively large burial monument is located in the south-western sector, which is closed to the public.

In 2011 scientific equipment believed to have belonged to Black was discovered during an excavation at the University of Edinburgh.

Sources

1. Joseph Black
2. Τζόζεφ Μπλακ
3. ^ Guerlac, Henry (1970–1980). "Black, Joseph". Dictionary of Scientific Biography. Vol. 2. New York: Charles Scribner's Sons. pp. 173–183. ISBN 978-0-684-10114-9.
4. ^ Lenard, Philipp (1950). Great Men of Science. London: G. Bell and Sons. p. 129. ISBN 0-8369-1614-X. (Translated from the second German edition.)
5. ^ Antonis Modinos (15 October 2013). From Aristotle to Schrödinger: The Curiosity of Physics. Springer International Publishing. p. 134. ISBN 978-3-319-00749-6.
6. ^ Eddy, Matthew Daniel (2008). John Walker, Chemistry and the Edinburgh Medical School, 1750-1800. London: Routledge.
7. 1,0 1,1 Φιόντορ Πετρούσοφσκι: «Блэк, Иосиф» (Ρωσικά)
8. Mary Weeks: Discovery of the elements. 1956, S. 523.
9. M. P. Crosland: The use of diagrams as chemical 'equations' in the lectures of William Cullen and Joseph Black. In: Annals of Science, Band 15, 1959, S. 75–90.
10. Ausländische Mitglieder der Russischen Akademie der Wissenschaften seit 1724. Joseph Black. Russische Akademie der Wissenschaften, abgerufen am 2. August 2015 (englisch).
11. Biographical Index: Former RSE Fellows 1783–2002. Royal Society of Edinburgh, archiviert vom Original am 25. Oktober 2017; abgerufen am 9. Oktober 2019.
12. (en) Henry Guerlac, Dictionary of Scientific Biography, vol. 2, « Black, Joseph », p. 173–183.
13. Son père était originaire de Belfast, et sa mère était issue d'une famille de vignerons de l’Aberdeenshire, en Écosse.