April 16, 1728: Joseph Black is born
Joseph Black (1728-1799)
Scientific field: Chemistry, Physics
Known for: Discovery of carbon dioxide, Latent heat, Specific heat
Joseph Black was a British chemist and physicist best known for the rediscovery of “fixed air” (carbon dioxide), the concept of latent heat, and the discovery of the bicarbonates.
In his investigations of the heating of magnesia alba (magnesium carbonate), Black anticipated Lavoisier and modern chemistry by indicating the existence of a gas, carbon dioxide, distinct from common air. Black’s account of his studies, published in 1756 as “Experiments Upon Magnesia Alba, Quicklime, and Some Other Alcaline Substances”, proved that the mild alkalies (carbonates) are causticized (become more alkaline) when they lose carbon dioxide and that absorption of this gas converts the caustic alkalies again to mild ones. Black found that carbon dioxide acts as an acid and is produced by fermentation, respiration, and the burning of charcoal, and he inferred its presence in the atmosphere.
At the University of Glasgow, Black’s studies ultimately led to his doctrine of latent heat. He noticed that when ice melts it takes up heat without undergoing any change of temperature, and he argued that this heat must have combined with the particles of ice and thus become latent. He verified this hypothesis quantitatively in 1761 and thereafter taught the doctrine. Although Black never published any detailed account of his work on latent heat, his friend James Watt doubtless was influenced by these ideas in his revolutionary construction of the condensing steam engine. Black also noticed that different bodies in equal masses require different amounts of heat to raise them to the same temperature, and so founded the theory of specific heats.
Black’s lectures were written out posthumously from his own notes, supplemented by those of his pupils, and published with a biographical preface by his friend and colleague John Robison in 1803 as “Lectures on the Elements of Chemistry, Delivered in the University of Edinburgh”.(1)
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