Joseph Black

Joseph Black (16 April 1728 – 6 December 1799) was a Scottish physicist and chemist. He made important discoveries, including magnesium, latent heat, specific heat, and carbon dioxide. His work helped scientists understand how heat and matter work together.

Black taught at two universities. He was a professor of anatomy and chemistry at the University of Glasgow for ten years, starting in 1756. Later, from 1766 until his death, he taught medicine and chemistry at the University of Edinburgh for more than thirty years.

Today, the chemistry buildings at both the University of Edinburgh and the University of Glasgow are named after him, showing how much his work meant to science.

Early life and education

Joseph Black was born near the river Garonne in Bordeaux, France. He was one of 12 children. His mother came from Aberdeenshire, and his father was from Belfast, Ireland, and worked in the wine trade. Joseph was taught at home until he was 12, then went to school in Belfast. At 18, he joined the University of Glasgow for four years, and later spent four more years at the University of Edinburgh studying medicine. While studying, he wrote a special project about using magnesium carbonate to help with kidney stones.

Scientific Studies

Chemistry

Chemical principles

Joseph Black studied chemistry using five basic ideas about matter: Water, Salt, Earth, Fire, and Metal. He added another idea, Air, after discovering a gas called fixed air, which we now know as carbon dioxide. This helped create a new area of science called pneumatic chemistry.

Black’s work focused on how these basic ideas mixed together. He used the word affinity to explain the force that kept these mixtures together. He taught his students at the University of Edinburgh using diagrams and experiments to show how to work with these affinities.

Analytical balance

When he was still a student, around 1750, Black made a very accurate tool called the analytical balance. It used a light beam balanced on a wedge, with pans on each end to hold samples or weights. This balance was much more precise than others at the time and became a key tool in chemistry labs.

Carbon dioxide

Black studied a gas made during many reactions. He found that heating limestone or treating it with acids produced a gas he called “fixed air.” He noticed this gas was heavier than normal air and did not let flames burn or support life. When this gas was bubbled through a solution of lime, it formed solid calcium carbonate. Black used this to show that carbon dioxide is made during animal respiration and when tiny living things ferment.

Heat

Main article: Heat § History

In 1756, Black began studying heat in detail.

Specific heat

Main article: Specific heat capacity § History

In 1760, Black discovered that when you mix two different substances at different temperatures, even if they have the same weight, the amount their temperatures change can be different. He explained this using an experiment: if you mix equal parts of water at 100 °F and mercury at 150 °F, the water warms up by 20 °F and the mercury cools down by 30 °F, but the amount of heat lost and gained is the same. This helped explain the difference between heat and temperature and introduced the idea that different substances can hold different amounts of heat.

Latent heat

Main article: Latent heat § History

In 1761, Black found that adding heat to ice at its melting point does not make the ice warmer, but turns it into more water. Similarly, adding heat to boiling water does not make the water hotter, but turns it into more steam. He concluded that the added heat had hidden away in these changes. This idea, called latent heat, was a big step in the science of heat and energy.

Black’s work on latent heat was very important. It helped start the science of thermodynamics. His discovery also helped improve the steam engine. Black became friends with James Watt, and supported Watt’s early work on steam power. Watt used Black’s ideas to make steam engines work better.

Professorship

In 1766, Joseph Black became the Professor of Medicine and Chemistry at the University of Edinburgh after his friend William Cullen moved there. Someone else, Alexander Stevenson, took over Black’s old job at the University of Glasgow.

Black focused fully on teaching and became very popular. More and more students attended his lectures for over thirty years. His classes were fun and easy to understand, using cool experiments and clear explanations. Students from all over the United Kingdom, its colonies, and Europe came to learn from him.

In 1783, Black helped start the Royal Society of Edinburgh. He also served as president of the Royal College of Physicians of Edinburgh from 1788 to 1790. Later, because of health problems, he had to reduce his work. By 1795, someone else helped him with his teaching, and he gave his last lecture in 1797.

Personal life

Joseph Black was a member of The Poker Club and had many close friends, including Adam Ferguson, David Hume, Adam Smith, and James Hutton. He lived in the Old Town and later used a house in Sciennes during the summer.

Black never married. He passed away at his home in Edinburgh in 1799 at the age of 71 and was buried in Greyfriars Kirkyard. In 2011, scientists found tools they thought belonged to Black during a dig at the University of Edinburgh.