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Unification achieved: William Cullen's theory of heat and phlogiston as an example of his philosophical chemistry

Published online by Cambridge University Press:  10 November 2006

GEORGETTE Taylor
GEORGETTE Taylor
Affiliation:
STS Department, UCL, Gower Street, London WC1E 6BT, UK. Email: [email protected].
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Abstract

William Cullen, lecturer in chemistry at Glasgow and Edinburgh Universities, spent many years formulating his own theory of heat and combustion, the most developed version of which appears in a little-known set of lecture notes of 1765. Cullen's theory is of particular interest to historians of chemistry as an example of his ideal of ‘philosophical chemistry’, an autonomous branch of natural philosophy distinct from the mechanical philosophy, with its own general laws and explanations of phenomena justified by observation. The theory assimilated Joseph Black's recent discovery of fixed air as well as Cullen's investigations of the generation of heat in chemical operations. It was formulated just one year before British chemists' sudden identification of new ‘airs’ was dramatically to change the field of phlogiston theory. The theory differs in important ways from any version yet discussed. It successfully brought both heat and elective attraction within its explanatory domain. It set out a causal hierarchy which reversed the usual pattern evinced in earlier sets of lecture notes, subordinating the mechanical to the chemical in the form of Cullen's theory of elective attraction. The paper argues that Cullen was attempting to bring the study of heat as well as combustion within the bounds of his ‘philosophical chemistry’ by means of his single unifying theory.

Type
Research Article
Information
The British Journal for the History of Science , Volume 39 , Issue 4 , December 2006 , pp. 477 - 501
Copyright
© 2004 British Society for the History of Science

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Footnotes

I would like to thank the AHRC, whose funding made this research possible. Also the staff of the Wellcome Library for the History and Understanding of Medicine and the Library of the Royal College of Physicians, Edinburgh, all of whom were unfailingly helpful on every occasion. All manuscript material is quoted by kind permission of these libraries. My thanks for their invaluable advice and constructive criticism are due to all those who read early drafts, but most particularly to Hasok Chang, Anna Simmons and the two anonymous BJHS referees. Thanks also to Simon Schaffer for his encouragement, and to my brother Hamish Ironside for his erudition. Finally, thanks also to my husband for his unflagging and invaluable support.