Joseph Black, teacher of genius

The many recountings of the life of Scottish inventor James Watt are generous in their praise for his development of a modern steam engine. Also frequently cited is the importance of Watt’s friendship with a man named Joseph Black, whose own achievements have stood the test of time.

For example, this from the German MTM Association (Methods-Time Measurement): “When James Watt had his low-pressure steam engine patented in 1769, he ushered in the greatest technological revolution in history.”

Or this, from the introduction to an article published by the Interesting Engineering website: “James Watt was one of the most important engineers and scientists in history. His work on the modern steam engine kick-started the entire Industrial Revolution.”

The most noteworthy, as Cosmos acknowledged a decade ago in an article about “17 molecules that changed the world”, was “the discovery and isolation of carbon dioxide… in the 1750s”.

Similarly, a paper by John B West published by The American Physiological Society in 2014 says: “The discovery of carbon dioxide by Joseph Black marked a new era of research on the respiratory gases.”

Black – one of 15 children – was born in Bordeaux, France, on 16 April 1728. His parents were both Scots who were involved in the wine trade.

At 12 he was sent to school in Belfast and at 16 entered the University of Glasgow – at first studying arts but later switching to medicine.

This brought him under the instruction of William Cullen who in 1747 “had instituted the first lectures in chemistry”, according to an article on Black prepared by the University. 

West’s paper notes that Black began studying alkalis “such as limewater that were thought to be useful in the treatment of kidney stones”. 

“When he studied magnesium carbonate, he found that when this was heated or exposed to acid, a gas was evolved that he called ‘fixed air’ because it had been combined with a solid material. 

“He showed that the new gas extinguished a flame, that it could not support life, and that it was present in gas exhaled from the lung. Within a few years of his discovery, hydrogen, nitrogen, and oxygen were also isolated.”

A feature of Black’s research was his use of accurate measurement tools. West says Black is “credited with inventing the first accurate analytical balance”.

Moving on from the discovery of carbon dioxide, West says, Black turned his attention to heat, “and he was the first person to describe latent heat, that is the heat added or lost when a liquid changes its state, for example when water changes to ice or steam.”

Enter James Watt, who came to Glasgow at the age of 18 and went to work for Black as an instrument maker. Black had returned to Glasgow in 1756 as a professor. 

West describes the pair’s relationship, quoting Black: “I soon had occasion to employ him to make some things… and found him to be a young man possessing most uncommon talents for mechanical knowledge and practice… which often surprised and delighted me in our frequent conversations together.”

West says Watt “was puzzled why so much cooling was necessary to condense steam into water, and Black realised that the answer was the latent heat. The resulting improvements in steam engines ushered in the Industrial Revolution.”

The University of Glasgow article says Black’s studies seem “to have stimulated the next phase of [Watt’s] work involving the concept of latent heat, and the first steps in calorimetry. Here again, it was the quantitative aspects of his work which led to his discoveries, particularly in the careful measurement of heat.”

It says Black “did similar work establishing the idea of latent heats of vaporisation, leading to the general concept of heat capacity or specific heat. These early steps in thermodynamics went on alongside James Watt’s developments of improved steam engines, and the two were in constant communication.”

Black remained a popular and influential scientist and teacher until his death in Edinburgh on 6 December 1799. Watt, credited with changing the world, died in Heathfield, England, on 19 August 1819.