Black, Joseph (1728–99), chemist, was born 16 April 1728 in Bordeaux, France, ninth child among eight sons and five daughters of John Black (1681–1767), wine-merchant from Belfast, whose family originally came from Scotland, and his wife Margaret, daughter of Robert Gordon of Hillhead, Aberdeenshire, who also worked in the Bordeaux wine trade. John Black settled in Bordeaux in 1699, bought houses, lands, and vineyards and remained there until 1756, when he returned to Blamont North (Ballintaggart), Co. Armagh. His grandfather John Black (1647–1726) was a merchant in Belfast, married to Jane Eccles, whose brother, Sir John Eccles, had been lord mayor of Dublin and had a street named after him. Two of his brothers, George and Samuel Black, were each mayor of Belfast several times.
As there was no suitable English-speaking school in Bordeaux, he was educated at home by his parents. At the age of 12 (1740) he was sent to Belfast to study classics under a Mr Sprot and became a pupil of the old Latin school in Church Lane. In 1746 he went on to study medicine and natural sciences in Glasgow. He took a great interest in chemistry, which was first taught in Glasgow by William Cullen, professor of medicine. Cullen recognised his keenness and ability and appointed him as a laboratory assistant. In 1751 Black moved to Edinburgh to complete his studies, but postponed his degree until 1754, to work on his thesis, De humore acido à cibis orto, et de magnefia alba: experiments on magnesia, quicklime and other alkaline substances. It was later published in several editions (1754–6) and earned him his reputation as a chemist. These investigations on magnesium carbonate led to his discovery of carbon dioxide, or what he called ‘fixed air’, so named because of its ability to fix itself into other solid substances. He was also the first to demonstrate the production of carbon dioxide by respiration, fermentation, and the combustion of carbon, thus inferring its presence in the atmosphere. His use of the chemical balance in his experiments paved the way for quantitative analytical chemistry.
When Cullen moved to Edinburgh (1756), Black was appointed his successor as professor of anatomy and chemistry at Glasgow university. While there he developed his fundamental theories of latent heat and specific heat, laying the foundation of thermal science. His ideas and discussions with the engineer James Watt influenced the development of the steam engine. He also lent Watt money to develop his invention. His dislike of the publicity associated with publishing, however, meant his work on latent heat was never published. An outline of the work he did publish is found in the Belfast Monthly Magazine (1809). Ten years later he again followed in the footsteps of Cullen and was appointed professor of medicine and chemistry at Edinburgh university (1766–97). At this stage he abandoned experimental research and concentrated on teaching and administration as well as his successful medical practice. His lectures, given with an elegant simplicity, attracted new students to chemistry and growing audiences. This popularisation of chemistry even became a fashionable amusement.
During his life he had many honours bestowed on him; membership of the Paris and St Petersburg academies of science, the Royal Society of Edinburgh, and the Royal College of Physicians, and associate of the Académie Royale des Sciences. He was first physician to George III in Scotland.
A handsome and reserved man with a liberal outlook, he was gentle, sincere, and generous. He never married but had a wide circle of friends, including William Cullen, James Watt, and James Hutton, father of British geology, who published The theory of the earth (1795). Ill health and asthma dogged him all his life, which curtailed his physical activities, with the exception of horse riding. Singing, playing the flute, and painting were his other talents. He approached death in the same careful way he had lived. It came to him peacefully 6 December 1799 at his home in Edinburgh, during a simple meal, a cup of milk remaining undisturbed on his knee. He was buried in Greyfriars churchyard, Edinburgh. During his life he amassed a sum of £20,000, which, with his property, was divided into 10,000 shares and apportioned in various amounts to his numerous relatives. After his death his academic notes were brought together as Lectures in chemistry (1803), which went through three editions in German.