Black, Joseph (1728-1799)

Scottish physicist and chemist. In 1754 he discovered carbon dioxide (which he called ‘fixed air’). By his investigations in 1761 of latent heat and specific heat, he laid the foundation for the work of his pupil James Watt.

In 1756 Black described how carbonates become more alkaline when they lose carbon dioxide, whereas the taking-up of carbon dioxide reconverts them. He discovered that carbon dioxide behaves like an acid, is produced by fermentation, respiration, and the combustion of carbon, and guessed that it is present in the atmosphere. He also discovered the bicarbonates (hydrogencarbonates).

Born in Bordeaux, France, Black qualified as a doctor in Edinburgh, where he became professor of chemistry.

He noticed that when ice melts it absorbs heat from its surroundings without itself undergoing a change in temperature, from which he argued that the heat must have combined with the ice particles and become latent. He also observed that equal masses of different substances require different quantities of heat to change their temperatures by the same amount, an observation that established the concept of specific heat capacity.