Black, Joseph

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Black, Joseph (1728-1799): Scottish Chemist.

Joseph Black was one of the greatest chemists of the eighteenth century. Although he published only two works during his lifetime, Black isolated carbon dioxide gas and did important research on the nature of heat. He was also a popular teacher of chemistry who instructed hundreds of medical students in Edinburgh and Glasgow.

Black was born on 16 January 1728 in Bordeaux, fourth of twelve children to a family wine trade. When he was twelve years old, Black was sent to a private school in Belfast to begin the study of Latin and Greek. In 1744 he began standard classes at the University of Glasgow; where he decided to pursue a career in medicine. He began with anatomy and chemistry classes under William Cullen. He spent three years as Cullen's assistant and a friendship developed that lasted until Cullen's death in 1790.

By 1752, Black moved to the more prestigious University of Edinburgh, where he also worked at the Royal Infirmary operated by the university. Black finished his M.D. degree in 1754 and published his dissertation, which, following the custom of the day, he had written in Latin. The brief dissertation was divided into two parts. The first, devoted to stomach acidity, fulfilled the requirement for medical content. Black's real interest lay in the second part, which discussed his experiments with magnesia alba, or magnesium carbonate. In this portion Black described his discovery that the application of distilled vinegar to magnesia alba caused a weight loss and release of "fixed air" or cardon dioxide. Black's work in these experiments involved careful measurement using balances, or quantitative research, which was another of his important contributions.

The following year Black read an expanded version of the second part of his dissertation before the Philosophical Society of Edinburgh. This version was published in the society's proceedings in 1756 and made Black's reputation. That same year William Cullen left the University of Glasgow to become chemistry professor at Edinburgh, and Black took the post his mentor had vacated. Black developed an enormously popular lecture course in chemistry at the university and established a thriving medical practice as well.

Around 1760, Black began experiments related to heat. He developed the concept of "latent heat" to explain the amount of heat required during melting and vaporization of various substances. Black never published this research, but his lectures about it have survived in the course notes taken by several students. In 1764, James Watt consulted Black about a problem in his repairs to a model Newcomen steam engine. Black served as a mentor to Watt for many years, as the younger man developed his own steam engine with its many improvements over previous models.

By 1766, Black left Glasgow for the position in chemistry at the University of Edinburgh that his old mentor Cullen gave up in favor of a post in medicine. Black, who never married, held this position until his death on 6 December 1799. Since he had formulated his research without reference to phlogiston, Black's work on gases and heat helped pave the way for the revolution brought to chemistry in the late eighteenth century by Frenchman Lavoisier, Antoine Laurent.

Further Reading:

Buchanan, Brown. "Joseph Black (1728-1799): Scottish Physician and Chemist." Practitioner 224(1980):663-666

Breathnach, "Joseph Black (1728-1799): An Early Adept in Quantification and Interpretation." Journal of Medical Biography 8 (2000):149-155

A.J. Wright

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