BLACK, JOSEPH Scottish chemist and phys icist, was born at Bordeaux, where his father—a native of Belfast but of Scottish descent—was engaged in the wine trade. He was educated at Belfast, and at Glasgow university. There he had William Cullen for his instructor in chemistry, and the relation between the two soon became that of professor and assistant rather than of master and pupil. In the thesis De humore acido a cibis orto, et magnesia alba, which he presented for his doctor's degree in 1754, he described his investigations in causticization, and anticipated Lavoisier and modern chemistry by indicating the existence of a gas distinct from common air, which he detected by using the balance. A fuller account of them was read before the Medical Society of Edinburgh in June 1755, and published in the following year as Experiments upon magnesia, quicklime and some other alkaline substances.
It is curious that Black left to others the detailed study of this "fixed air" he had discovered. Probably the explanation is pres sure of other work. In 1756 he succeeded Cullen as lecturer in chemistry at Glasgow, and was also appointed professor of anatomy, though that post he was glad to exchange for the chair of medicine. He also practised as a physician. Moreover, his attention was engaged on studies which ultimately led to his doctrine of latent heat. He noticed that when ice melts it takes up a quantity of heat without undergoing any change of tempera ture, and he argued that this heat, which, as was usual in his time, he looked upon as a subtle fluid, must have combined with the particles of ice and thus become latent in its substance. This hypothesis he verified quantitatively by experiments performed at the end of 1761. In 1764, with the aid of his assistant, William Irvine (1743-87), he further measured the latent heat of steam, though not very accurately. This doctrine of latent heat he taught in his lectures from 1761 onwards, and in April 1762 he described his work to a literary society in Glasgow. But he never published any detailed account of it, so that others, such as J. A. Deluc, were able to claim the credit of his results. In the course of his enquiries he also noticed that different bodies in equal masses require different amounts of heat to raise them to the same temperature, and so founded the doctrine of specific heats; he also showed that equal additions or abstractions of heat produced equal variations of bulk in the liquid of his thermometers. In 1766 he succeeded Cullen in the chair of chemistry in Edinburgh. He died in Edinburgh on Dec. 6, 1799 (not on Nov. 26 as stated in Robison's life) .
Apart from the work already mentioned he published only two papers during his lifetime—"The supposed effect of boiling on water, in disposing it to freeze more readily" (Phil. Trans., 1775 ), and "An analysis of the waters of the hot springs in Iceland" (Trans. Roy. Soc. Ed., After his death his lectures were written out from his own notes, supplemented by those of some of his pupils, and published with a biographical preface by his friend and colleague, Professor John Robison 0739-1805), in 1803 as Lectures on the Elements of Chemistry, delivered in the University of Edinburgh.