Black, Joseph (1728-1799), a Scottish chemist and physicist, is best remembered for discovering carbon dioxide and the bicarbonates. He is also known for his research into latent heat (the energy needed to change a substance from a solid to a liquid or from a liquid to a gas) and specific heat (the amount of heat needed to raise the temperature of one gram of a substance one degree Celsius).
Born in Bordeaux, France, where his father worked in the wine trade, Black studied medicine at the universities of Glasgow and Edinburgh in Scotland. He not only practiced as a physician but also became chairman of the department of medicine at the University of Glasgow, where he had earlier taught both chemistry and anatomy. Black later became professor of medicine and chemistry at Edinburgh University.
In 1754, while working with magnesium carbonate, Black detected carbon dioxide, which he called “fixed air,” as a gas distinct from ordinary air. He also found that carbon dioxide acts as an acid with alkaline substances; is a product of fermentation, respiration, and the burning of charcoal; and is present in the atmosphere. In 1756, a published account of his work appeared under the title “Experiments upon Magnesia Alba, Quicklime, and Some Other Alcaline Substances.”
Further studies led Black to the concept of latent heat. He observed that as ice melts, it absorbs heat without changing in temperature. He reasoned that the heat must have combined with the ice particles and become latent, or hidden. Black's observation that equal masses of different substances require different amounts of heat to raise them the same temperature degrees led to his development of the theory of specific heat.