Elements, Instruments, and Menstruums: Boerhaave’s Imponderable Fire Between Chemical Masterpiece and Physical Axiom

The chapter examines Herman Boerhaave’s (1668–1738) influential account of fire and heat, expounded in his 1732 Elementa chemiae, in light of the changing relations between chemistry and natural philosophy during the late seventeenth and early eighteenth centuries. Going back to the 1660s and to Robert Boyle’s critique of chemical analysis and the nature of elements, the chapter explores the tensions and challenges inherent in Boerhaave’s view of elements and instruments—fire was both—as well as his ideas about menstruums and solution chemistry. Particular attention is paid to his consideration of fire as an imponderable agent of material change against the backdrop of mechanistic and materialistic trends in matter theory. The contributions of two chemists and members of the French Royal Academy of Sciences, Samuel Duclos (1598–1685) and Wilhelm Homberg (1652–1715), who developed theoretical and experimental programs employing burning lenses and mirrors, are evaluated as part of the story. These contextual reconstructionsillustrate the dynamics of change among diverging notions of elements, instruments, analysis, composition, and material change more generally, as these entities and categories straddled the shifting perimeters of the physical–chemical divide around the turn of the eighteenth century.