Joseph Black
Scottish physicist and chemist who discovered latent heat and carbon dioxide.
Joseph Black (16 April 1728 – 6 December 1799) was a Scottish physicist and chemist whose discoveries fundamentally shaped modern chemistry and thermodynamics. He is best known for identifying magnesium, carbon dioxide (which he termed “fixed air”), and for establishing the concepts of latent heat and specific heat. Born in Bordeaux, France, to parents involved in the wine trade, Black was educated at home until age twelve, then attended grammar school in Belfast. He entered the University of Glasgow in 1746, studying for four years before moving to the University of Edinburgh for another four years of medical studies. His doctoral thesis examined the treatment of kidney stones using magnesium carbonate. In 1750, while still a student, Black developed a highly precise analytical balance, using a lightweight beam on a wedge-shaped fulcrum, which became a crucial laboratory instrument. His research into carbon dioxide revealed that limestone, when heated or treated with acid, released a denser gas that did not support flame or life; he also demonstrated that this gas was produced by respiration and fermentation. Black’s work on heat began around 1756. He showed that different substances require different amounts of heat to raise their temperature by the same degree, thus distinguishing heat from temperature and introducing specific heat capacity. Crucially, he discovered latent heat: the heat absorbed or released during phase changes without a temperature change, such as ice melting or water boiling. This theory, a foundation of thermodynamics, proved vital for James Watt’s improvements to the steam engine. Black was professor of anatomy and chemistry at Glasgow from 1756 for ten years, then professor of medicine and chemistry at Edinburgh from 1766, teaching for over three decades. The chemistry buildings at both universities bear his name.
- field
- Physics and chemistry
- nationality
- Scottish
- known_for
- Discoveries of magnesium, latent heat, specific heat, and carbon dioxide
Lore & Background
Joseph Black, born in Bordeaux, France, was the sixth of twelve children. He was initially taught at home, later attending a grammar school in Belfast. His doctoral research focused on the medicinal use of magnesium carbonate for kidney stones. Black’s defining scientific contributions include the discovery of carbon dioxide, which he termed “fixed air,” and his foundational work on heat. He demonstrated that limestone, when heated or treated with acid, releases a dense gas that neither supports flame nor animal life. Crucially, he established that different substances possess distinct capacities for heat, a concept now known as specific heat. His most celebrated achievement was the theory of latent heat, showing that heat applied to ice at its melting point does not raise its temperature but instead converts ice to water, and similarly, heat applied to boiling water produces steam without a temperature increase. This theory is considered the beginning of thermodynamics and was instrumental in the development of the steam engine. Black also invented a highly accurate analytical balance, which became a standard laboratory instrument. He taught at the University of Glasgow and later at the University of Edinburgh, where chemistry buildings bear his name.
Reader's Guide
Joseph Black's contributions fundamentally shaped modern chemistry and thermodynamics. His discovery of carbon dioxide, which he called 'fixed air,' advanced pneumatic chemistry and demonstrated that a gas could be chemically distinct from air. His development of the analytical balance provided a precise tool for quantitative experiments. Most significantly, his concepts of specific heat and latent heat clarified the distinction between heat and temperature, laying the groundwork for thermodynamics. His clear teaching and use of experiments popularized chemistry, and hundreds of students preserved his lectures in notebooks, disseminating his ideas widely. His legacy is commemorated by chemistry buildings named after him at both the University of Edinburgh and the University of Glasgow.
Did You Know?
- He discovered that limestone heated or treated with acids yields a gas he called 'fixed air' (carbon dioxide), which is denser than air and does not support flame or animal life.
- Black's theory of latent heat marks the beginning of thermodynamics and was important for the development of the steam engine.
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