Scottish physician and chemist · 1728–1799
Joseph Black
Joseph Black showed in 1755 that magnesia contained an element different from lime, the first step toward magnesium. In the same work he discovered carbon dioxide.
How Magnesium was found
For his medical thesis Black studied magnesia alba, a remedy for indigestion. He heated it and weighed it carefully, and found that it lost weight by giving off a gas he called “fixed air”, now known as carbon dioxide.
He showed that magnesia and lime, though similar, form different salts, so they must contain different substances. The metal itself, magnesium, was not isolated until Humphry Davy’s work in 1808, but Black’s careful weighing first marked it as distinct.
Life and career
Born 1728 · Died 1799
Black was born in Bordeaux to a Scottish-Irish wine merchant family and studied at Glasgow and Edinburgh. He taught medicine and chemistry at both universities.
He discovered latent heat, the heat absorbed when ice melts or water boils without changing temperature, and specific heat. His friend and instrument maker James Watt used these ideas to improve the steam engine.
Also known for
- Discovery of carbon dioxide
- Latent heat and specific heat
Discovered in the same era
Other elements identified within ten years of 1755.