Joseph Black

Chemist, born in Bordeaux, SW France. He studied at Belfast, Glasgow, and Edinburgh, and in 1756 showed that the causticity of lime and alkalis is due to the absence of the ‘fixed air’ (carbon dioxide) present in limestone and the carbonates of the alkalis. He evolved the theory of ‘latent heat’, on which his scientific fame chiefly rests, and founded the theory of specific heats. In 1766 he became professor of medicine and chemistry at Edinburgh.

Joseph Black

Joseph Black (April 16, 1728 - December 6, 1799) was a Scottish physicist and chemist.

In 1746, he entered the University of Glasgow.

In the late 1750's he made an apparently innocuous experiment. He heated during the same time in an oven the same quantity of water and mercury and measured its respective temperatures. He concluded that heat was a weightless fluid, invisible and indestructible and, according to his experiment, different materials had different capacities of absorbing and keeping heat. The interpretation of this experiment had disastrous consequences on the use of thermometers because its measurement may not be reproducible if the materials used in different thermometers were different. In other words, the measurement of the thermometers made with different materials (different glass, mercury with different purity...) coincide in the melting point of ice and in the boiling point of water. However, the values not necessarily coincide in the intermediate points as the materials behave differently when they are heated or cooled.

In 1757 he was appointed Regius Professor of the Practice of Medicine at the University of Glasgow.

In 1761 he discovered that ice absorbs heat without changing temperature when melting. From this he concluded that the heat must have combined with the ice particles and become latent.

Between 1759 and 1763 he evolved that theory of "latent heat" on which his scientific fame chiefly rests, and also showed that different substances have different specific heats.

In 1755 he discovered that magnesium was a chemical element.

He was a member of the Poker Club and associated with David Hume, Adam Smith and the literati of the Scottish Enlightenment.