Quicksilver and quicksilver-based drugs were widely used as cure-alls throughout the seventeenth and eighteenth centuries. This paper is concerned with the question how mercury, as an alchemical material, remained integrated in eighteenth-century medicine. It is based on the hypothesis that even though alchemy itself became increasingly associated with deceit, alchemical materials remained of crucial importance in medicine, and that the integration of chemical experiment in academic medicine strengthened the position of mercury in medical theory rather than undermining it.

Mercury was commonly seen as a live-giving substance that could penetrate and cleanse even the smallest structures in the body, and hence as a powerful drug. Mercury-based drugs were widely used to treat venereal diseases, skin problems and general physical imbalances. However, mercury was also known to be potentially dangerous, and was associated with quacks and gold-seeking alchemists. Nonetheless, practical chemistry –taking most of its methods and materials from traditional alchemy - was steadily integrated in academic research and teaching from the seventeenth century, and experiment and reason were increasingly combined to develop medical theory.

Curiously, this does not seem to have changed the use of mercury in medicine considerably, as mercury-based drugs were still found in abundance in early nineteenth-century pharmacopeia and medicine chests. The continued use of mercury in drugs reveals the tensions surrounding the eighteenth-century use of mercury. On the one hand traditional transmutational alchemy was dismissed by someone like the famous professor of chemistry and medicine Herman Boerhaave (1668-1738) and ridiculed by his follower Abraham Kaau Boerhaave. On the other hand, mercury was still considered one of the most important medical materials. This paper considers how eighteenth-century laboratory practice influenced the role of mercury in contemporary medical theory.

The focus here is on Leiden University, where a chemical laboratory was first installed in 1669, and where Boerhaave experimented with mercury extensively in the 1730s. This paper shows how the results of these mercury experiments in the eighteenth-century academy were integrated in academic medical theory, and investigates whether this actually changed the use of mercury in drugs.