Johannes Bohn at the University of Leipzig

‘Jo. Bohnius, professor of Leipsic, deserves to be read again, and again. His Dissertat. Chemico-Phys. published in 8o, beside an uncommon reading, shew that he has made a good number of experiments. And as to his reasonings, nobody goes beyond him. His treatise de Acido & Alkali, is excellent; and had let a deal of light into the Affair.’

Herman Boerhaave, A new method of chemistry (London, 1727), p. 47.

Bohn portrait.
Courtesy of the National Library of Medicine.

Johannes Bohn (1640-1718), had studied medicine at Jena and Leipzig before being appointed Professor of Anatomy at Leipzig where he would subsequently be appointed Stadtphysikus. It was while he was at the University of Jena that he was prevailed on to publish his writings on chymistry and he duly divided his text into four main parts: the first concerned the philosophical underpinning of chymistry; the second dealt with the pharmaceutical purpose; the third examined its mechanical/artisanal applications; and, finally, the fourth explored the process of transmutation. As Moran (2006) says, all four parts were united by a common theme – that ‘the end and means of chemistry were the same’. The reasons for Boerhaave’s recommendation of Johannes Bohn’s Dissertationes chymico-physicae (of which Worth had not one but two copies), are not hard to see. As Powers (2007) suggests, what attracted Boerhaave to Bohn’s text was its philosophical approach, an approach which Boerhaave would later make his own. In addition, Bohn’s mechanistic approach, coupled with his hero worship of Boyle, chimed well with Boerhaave’s own inclinations. As Clericuzio (2000) demonstrates, Boyle’s influence spread far and wide and is clearly seen in the corpuscular theory of Bohn at Leipzig and Friedrich Hoffmann at Halle.

As the title suggests, Bohn’s text was based on the physics dissertations at the University of Leipzig and it therefore allows the reader to reconstruct Bohn’s course of chemical teaching at the medical faculty of Leipzig. There were fifteen sets of dissertations, loosely based on ‘chemical’ subjects, and each of these contained up to thirty theses. These theses were the academic exercises that Bohn’s students had to undergo as part of their medical training at Leipzig and the emphasis was on definition and logical conclusion. Some indeed focussed on chemical processes such as calcination but in the main the emphasis was on theory rather than practice. Despite this the work provides much information about the instruments used at Leipzig and their many uses. For Bohn ‘instruments’ could mean many things – not just the physical objects used in experiments but also the elements of fire, water, air and earth.

Nicolas Lemery, A course of chymistry… (London, 1698), Table V.

Sources

Boerhaave, Herman (1727) A new method of chemistry (London).

Moran. Bruce T. (2005), Distilling Knowledge. Alchemy, Chemistry, and the Scientific Revolution (Harvard University Press).

Powers, John C. (2006), ‘Chemistry Enters the University: Herman Boerhaave and the Reform of the Chemical Arts’, History of Universities 21 (2) 77-116.

Powers, John C. (2007) ‘Chemistry without principles: Herman Boerhaave on Instruments and Elements’ in Lawrence M. Principe (ed.) New Narratives in Eighteenth-Century Chemistry (Dordrecht), pp 45-61.