BLACK, JOSEPII ( 1728-99). A Scottish chem ist. He was born in Bordeaux, France, where his father was engaged in the wine-trade. Both his parents were of Scotch descent, but natives of Belfast, whither their son was sent for his edu cation in 1740. in 1746 lie entered the Uni versity of Glasgow; in 1751 he went to Edin burgh to complete his medical course, and in 1754 took his degree. His thesis on the nature of the mild and caustic alkalies and alkaline earths contained his first contribution to chem ical science. in those days the transformation by heat of a mild alkali (a metallic carbonate) into the corresponding caustic alkali (an oxide, or hydroxide) was interpreted on the hypothesis that the mild alkali combines with the fiery principle called phlogiston, and thus the caustic alkali is produced. Black showed. however, that the transformation %vas accompanied by a loss of weight, and that during the transformation an airiform substance escaped from the mild alkali. This aeriform substance he found to be different from atmospheric air, and gave it the name of fixed air. Thus the existence, both in the free state and in combination, of a gas different from air —namely, carbonic acid—was first clearly estab lished by Black. Black succeeded Cullen as pro
fessor of anatomy (which branch he afterwards exchanged for medicine) and lecturer on chem istry in Glasgow. Between 1759 and 1763 he evolved that theory of 'latent heat' on which his scientific fame chiefly rests, and which formed the immediate preliminary to the next great stride in discovery by his pupil and assistant, ,Tames Watt. In 1766 Cullen was appointed to the chair of theoretical medicine in Edinburgh, and Black succeeded him in the chair of chem istry. Thenceforth he devoted himself chiefly to the elaboration of his lectures, in which he aimed at the utmost degree of perspicuity, and with perfect success. Black published: Experi ments on Magnesia, Quicklime, and Other AB•a line Substances; Observations on the More Ready Freezing of Water that Has Been Boiled; and Analysis of the Waters of 'ome Boiling Springs in Iceland. his Lectures on the Elements of Chemistry was published after his death, by Robinson (2 vols., London, 1803). Consult Brougham, Lives of Philosophers of the Time of George M. (London and Glasgow, 1855).