Joseph Black (1728–1799)

Black presents a genuinely unusual case in the history of science: a figure whose direct written output was famously sparse, and whose enormous influence was transmitted chiefly through teaching rather than publication. This article treats that teaching-centred legacy as a real and well-documented fact about how science actually spread in his era, rather than a lesser or secondary form of achievement compared to Hutton's or Smith's published books.

A cosmopolitan upbringing

Joseph Black was born in Bordeaux in 1728, not Scotland — a detail that sometimes surprises readers, though his family's roots and his own career were thoroughly Scottish. His father was a Belfast-born wine merchant working in the Bordeaux trade, and his mother came from an Aberdeenshire family also connected to the wine business; Black was the sixth of twelve children in this prosperous, multilingual household. Sent to grammar school in Belfast at twelve, he began his university education at Glasgow in 1746, where he studied under the influential chemistry lecturer William Cullen — a formative relationship Black would later, in effect, complete the circle of by succeeding Cullen directly in the chemistry chair at Edinburgh two decades later.

Fixed air: the birth of quantitative chemistry

Black's medical doctoral thesis, completed at Edinburgh in 1754, investigated the use of magnesium carbonate ("magnesia alba") in treating kidney stones — unglamorous clinical research that happened to put him directly in contact with the chemical substance at the centre of his most important discovery. Investigating magnesia alba and related substances like limestone, Black found that heating or treating them with acid released a distinct gas — which he termed "fixed air," now understood as carbon dioxide — that was measurably different from ordinary atmospheric air: denser, incapable of supporting flame or animal respiration, and precipitable out of lime-water as solid calcium carbonate, giving him a way to measure its presence and quantity precisely.

Established/Documented, and genuinely significant to the history of science: what made this work exceptional for its era was not simply the discovery itself but Black's method. He weighed his reactants and products carefully, establishing that a defined, measurable quantity of gas was involved rather than treating the phenomenon in loosely qualitative terms — an approach that helped inaugurate quantitative, measurement-based chemistry as a discipline. The French chemist Antoine Lavoisier, later a towering figure in the field in his own right, is recorded as directly acknowledging the "important revolutions" Black's discoveries had caused in the sciences.

Latent heat, specific heat, and the road to thermodynamics

Beginning around 1757 and continuing into the early 1760s, Black turned his careful, measurement-based approach to the study of heat itself. He observed a puzzling and important fact: applying continuous heat to ice at its melting point does not raise its temperature at all — it simply converts more of the ice to liquid water at the same temperature — and the same pattern holds for boiling water converting to steam. Black concluded that this heat had not disappeared but had become "latent," absorbed into the physical change of state itself rather than registering as a temperature rise. This is the origin of the modern concept of latent heat.

He complemented this with the related concept of specific heat capacity — recognising that equal masses of different substances (his own experiments compared water and mercury) require different quantities of heat to produce the same rise in temperature. Established/Documented: these two related insights are now widely regarded by historians of science as marking the effective beginning of thermodynamics as a field — a genuinely major theoretical contribution. It is a striking fact about Black's career that he himself formally published very little of this work; it survived and spread chiefly through the detailed lecture notes his students took down and carried with them.

The Watt connection: theory meets the Industrial Revolution

Established/Documented, and one of the more concrete links between Enlightenment science and the Industrial Revolution: Black's friendship with James Watt began around 1757 at the University of Glasgow, where Watt worked as an instrument maker. Black provided Watt with both intellectual engagement and, at points, direct financial support, and Watt's own later account of his thinking credits his understanding of Black's latent heat theory as a genuine, practical spur to his critical improvements on Thomas Newcomen's existing steam engine design — specifically, insight into why so much heat (and therefore fuel) was being wasted in the repeated heating and cooling of the engine's cylinder, which led Watt toward his separate-condenser design. This is not a vague, ceremonial connection between two famous contemporaries; it is a documented case of abstract thermal theory feeding directly into one of the most consequential mechanical inventions in history.

A teacher first, a publisher second

Black held professorships first at Glasgow (from 1757) and then, succeeding his own teacher Cullen, at Edinburgh from 1766 until poor health forced his retirement from active lecturing in the mid-1790s. By most accounts he was an extraordinary teacher: his lectures, delivered in a distinctive quiet but exceptionally clear voice, drew hundreds of students annually by the 1790s, and he is estimated to have taught something in the region of 5,000 students across his career, using careful experimental demonstration to make chemistry accessible even to relatively young students. Many of his former pupils went on to hold chemistry professorships themselves at Cambridge, Oxford, Glasgow, and Edinburgh, meaning Black's specific approach to and understanding of chemistry propagated across Britain's universities largely through this teaching lineage rather than through his own printed output.

Shared/Traditional, but well supported by the documented pattern of his career: Black's reluctance to publish is generally understood as reflecting a perfectionist temperament rather than any lack of material or confidence — he continued refining and re-testing his ideas for years, and much of what is now attributed to him as settled science was, during his own lifetime, known chiefly through student lecture notes circulating informally rather than through his own formal papers.

Within the Scottish Enlightenment circle

Black was closely connected to the leading figures of the Scottish Enlightenment in Edinburgh, maintaining real friendships with Adam Smith, David Hume, and geologist James Hutton — the last of whom he was buried near, in Greyfirars Kirkyard, after his death. He was a founding member of the Royal Society of Edinburgh in 1783 and served as President of the Royal College of Physicians of Edinburgh from 1788 to 1790, reflecting his standing within both the medical and broader scientific establishment of the city.

Black and the Americans

established Franklin's host. The literary historian Andrew Hook, in Scotland and America (1975), places Black in the circle that entertained Benjamin Franklin on both his Scottish visits. In 1759 Franklin met Black alongside Hume, Kames, Robertson, Cullen and the Monros. When he returned in 1771, Black was a guest at the large dinner Hume gave in his honour and again at Adam Ferguson's a few days later. Franklin's friendships in this circle opened Edinburgh to the American medical students he sponsored.

established Teacher of the Philadelphia doctors. Hook lists Black among Benjamin Rush's teachers in 1766–68, with Cullen, Monro secundus, Russell and Gregory. Rush and the other Edinburgh-trained Americans, Morgan, Shippen and Kuhn, became professors in the Philadelphia medical school founded in 1765 on the Edinburgh model, so Black's chemistry, taught inside the medical course, reached America through the men who built its first medical faculty.

established The book in America. Black's lectures appeared in print only after his death, edited by John Robison. Hook records an American edition of the Lectures on the Elements of Chemistry at Philadelphia in 1806–07, part of a wave of American reprints of Scottish Enlightenment works after the Revolution. In 1829 Mitchell King, addressing the centenary of the St Andrew's Society of Charleston, praised Black as the man who had "paved the way for the splendid achievements of modern chemistry" (as quoted by Hook). When the Boston scholar George Ticknor visited Edinburgh in 1819, Walter Scott pointed out to him the houses of the old Enlightenment figures, Black's among them.

Death and an orderly legacy

Black's health declined from 1793 onward; Charles Hope was appointed as a co-professor to share his teaching duties in 1795, and Black delivered his final lecture in 1797. He died peacefully at his Edinburgh home in December 1799, aged 71, having never married. A small, characteristic detail: he left a substantial estate — reportedly around £20,000, a considerable sum for the period — which he arranged to be divided with precise, methodical care among his beneficiaries, in a manner biographers have noted as entirely consistent with the exacting, careful habits of mind that defined his scientific work.

Modern legacy

Black's reputation today rests on a genuinely substantial foundation: the identification of carbon dioxide as a distinct chemical substance through rigorous quantitative method, and the theoretical groundwork of latent and specific heat that underpins modern thermodynamics — achievements that, combined with his documented direct influence on Watt's steam engine improvements, place him among the most consequential figures of the Scottish Enlightenment's scientific wing, even though his own name is less widely known today than Smith's or Hutton's. A lunar crater bears his name, and a 2011 archaeological excavation at the University of Edinburgh recovered scientific instruments attributed to his own laboratory work — tangible physical evidence, more than two centuries later, of the meticulous experimental practice that defined his career.

• Joseph Black was born in Bordeaux, France, not Scotland — though his family and career were thoroughly Scottish.
• His MD thesis on treating kidney stones with magnesium carbonate led, almost by accident, directly to his discovery of carbon dioxide.
• He taught an estimated 5,000 students over his career at Edinburgh, and it was largely through their notes — not his own published papers — that his most important ideas spread.
• His friendship with a young Glasgow instrument-maker, James Watt, helped shape the theoretical understanding behind Watt's crucial improvements to the steam engine.
• Antoine Lavoisier, one of the most celebrated chemists in history, personally credited Black with causing "important revolutions" in the sciences.
• He designed an unusually precise analytical balance while still a student — an instrument that became a standard piece of laboratory equipment.
• He is buried in Greyfriars Kirkyard, Edinburgh, near his friend and fellow Enlightenment figure James Hutton.
• Benjamin Franklin met him in Edinburgh on both of Franklin's Scottish visits, in 1759 and 1771.
• Despite his enormous scientific influence, he published remarkably little in his own lifetime, a trait biographers attribute to perfectionism rather than a lack of ideas.

1. "Black was a minor figure overshadowed by Smith and Hutton." This article makes the case for the opposite reading: measured by direct student influence and later scientific consequence, his impact was arguably at least as large, even if his personal fame has not endured as widely.
2. The exact extent of Black's direct financial support of Watt varies somewhat between sources in specific figures; this article states the relationship and its intellectual influence as solidly documented while treating precise financial details with appropriate caution.
3. His reluctance to publish is treated here as a matter of documented biographical pattern and reasonable historical inference (perfectionism) rather than a fully resolved psychological explanation.