Chemistry without Principles: Herman Boerhaave on Instruments and Elements

Abstract

One of the more curious phenomena in the history of eighteenth-century chemistry was the reemergence of the four Aristotelian elements (fire, air, earth, and water) and of the alchemical notion of chemical “menstrua,” and the recasting of these five as “instruments.” These five instruments were defined as tools which the chemist utilized to instigate or prevent specific motions in matter during chemical operations. As such, the instruments and their specific properties occupied a prominent place in many pedagogical presentations of chemistry and were also the subject of theoretical discussion and experimental research. While some eighteenth-century chemists and more modern historians have referred to the “instruments” as “elements” (or “instrumentelements”), they were not elements in the traditional, Aristotelian sense. They did not (as the Aristotelians held) enter into the composition of all bodies, and in fact, the extent to which the instruments, especially “air” and “fire,” combined chemically with any other body was very much a topic for debate. In the seventeenth century, the earliest discussions by Daniel Sennert (c. 1620s) and the early university lectures of Georg Stahl (c. 1680s) clearly placed the instruments within the context of understanding the mechanisms or natural philosophy of chemical operations as distinct from problems of composition. Derived from this context, the instruments in the eighteenth century represented a relatively novel shift in the interests of philosophically-minded chemists towards problems regarding the action and mechanisms of chemical operations.