6.4 The Edinburgh professorship
Whytt, the Edinburgh professor of medicine, died in 1766 and Cullen was chosen to succeed him, largely with the aim of freeing the chemistry chair for Black. Black's transfer to Edinburgh was well received, and he fulfilled these expectations by being an excellent and popular lecturer. However, the Edinburgh chair also marked the end of his active research. One looks in vain for any sequel to his research on magnesia or his work on heat. With hindsight, foreshadowings of this change can be seen in Black's Glasgow period. He refused to publish his work on heat, and it was only made public when an unauthorised version, based on his lectures, appeared in 1770. Furthermore, in his last years in Glasgow, most of the research work was done by his assistants, William Irvine and John Robison.
However, the reasons are not too hard to find. He did not draw a salary as a professor, but had to rely on his lecture fees, and hence the number of students attracted to his course. Black's stock-in-trade was the elegant (rather than spectacular) lecture demonstration. With over 120 lectures to prepare and deliver between November and May, it doubtlessly reduced Black's scope for research, given his indifferent health. Black had become increasingly worried about his health – he had a bad chest – and probably felt that he did not have to prove his talents in chemistry now he had achieved his ambition of an Edinburgh chair.
Furthermore, he was an active physician, and while his private practice was small, he was also a manager of the Royal Infirmary and eventually a ‘Physician to the King in Scotland’, in addition to his work on the sixth to eighth revisions of the Edinburgh Pharmacopoeia.
His medical work was overshadowed by his growing role as an adviser to industry. To quote Robert Anderson, a leading authority on Black:
Black was consulted by a considerable number of industrialists on an extraordinary wide range of topics. In the surviving correspondence these include sugar refining, alkali production, bleaching, ceramic glazing, dyeing, brewing,metal corrosion, salt extraction, glass making, mineral composition, water analysis and vinegar manufacture. In addition his opinion was sought on agricultural matters. (Anderson, 1986, p. W7)
For instance, Black suggested that caustic potash (potassium hydroxide), prepared by the action of quicklime on potash, was a better bleach for linen than potash or sour milk. At first, the authorities were concerned that caustic potash would weaken the cloth, but the Irish Linen Board permitted its use in 1770.
Black never changed the structure of his lectures from his arrival in Edinburgh until his retirement 30 years later. While he updated individual items over the years, the unchanging structure became an obvious handicap in a period when chemistry was transformed. Clearly, the pressure on Black's time and his poor health partly explain the lack of any thorough revision, but it was also a reflection of Black's lack of interest in theoretical chemistry. He presented the phlogiston theory propagated by the English pneumatic chemists in his lectures without any great enthusiasm; their speculative conjectures were not to his taste. However, he was equally chary of the new chemistry from France, especially its systematic nomenclature.
The agent of change was Sir James Hall (1761–1832), a pupil of Black and James Hutton, who visited Paris in 1786. The earlier influence of an uncle and the heady experience of meeting Antoine Lavoisier (1743–94) converted Hall to the new chemistry. On his return to Scotland, he gave a paper to the Royal Society of Edinburgh on ‘M. Lavoisier's new theory of chemistry’ in the spring of 1788. Hutton defended the phlogiston theory in a later paper, but Black was characteristically silent. However, Lavoisier wrote to Black in September 1789 to inform him that he had been elected a foreign member of the French Academy of Sciences. It appears from a second letter from Lavoisier in July 1790 that Black had spoken guardedly in favour of Lavoisier's ideas. In a warm response to this second letter, Black declared his support for Lavoisier's chemistry, despite a few ‘difficultys’, and confirmed that he had begun to teach it in his lectures (text of letter in Donovan, 1979, p. 245).
Although Black was now in his sixties, his eloquence and his dexterity with apparatus could still command the admiration of Henry Brougham (later Baron Brougham) in 1796. This was the last course Black delivered, and he handed his lecturing duties over to his former student Thomas Charles Hope (1766–1844), who had been converted to Lavoisier's teachings by Sir James Hall in 1788. Black's health now began to fail altogether, and he died suddenly in 1799.
Black had built up the reputation of the teaching of chemistry at the University of Edinburgh, but it did not continue to prosper after his death. Part of the blame must be laid at the feet of his successor, Hope, who has been described as ‘dull, pompous and uninspiring’ (Anderson, 1986, p. 112). The Edinburgh tradition of teaching and lecture demonstrations to the exclusion of original research meant that it was unable to meet the challenge from the research-based German universities, most notably Giessen, in the 1840s.
Black's failure to prepare Edinburgh for the nineteenth century, and his personal failure to build on his initial achievements, can be traced to his indifferent health and his personality. Adam Smith once described his close friend as ‘cool and steady’ (Mossner and Ross, 1977, p. 207). Black was a cautious and fastidious man, with a desire for precision, who was not given to enthusiasm and rash actions, amongst which he appears to have numbered scientific publications. It is significant that his only important publication, ‘Experiments upon magnesia alba’, was a direct consequence of his MD thesis. This unfortunate mixture of indolence and coolness limited Black's contribution to the Chemical Revolution.
Black's work on latent heat laid the foundations for Lavoisier's theory of heat as a weightless chemical element, caloric. But Black was more than an intellectual bridge between Newton and Lavoisier. By treating heat as a measurable quantity, which could be transferred from one body to another, Black paved the way for the development of thermodynamics, the science of heat, in the nineteenth century.