Over the past two decades, it has become increasingly clear that alchemy, chemistry and medicine were still deeply intertwined in the early eighteenth century. Mostly rhetoric attempts by scholars to establish chemistry as a respectable, transparent academic discipline and renounce alchemy as its obscure predecessor were only partly successful. This latter phenomenon appears to have been particularly strong in the northern Netherlands, even though – or maybe because – many alchemists from the German lands temporarily lived and practiced in the Netherlands.
Very little is known about Dutch alchemists in the first half of the eighteenth century, and that is why I was rather surprised to find a Dutch manuscript on alchemy from 1741 in Leiden University’s special collections. It is signed ‘op Grootenburg octob: 18, 1741,’ and a search for Grootenburg quickly led me to Burghard de Groot (1661/2-1744), who left a number of illustrated Dutch alchemical manuscripts. Grootenburg was probably De Groot’s house on the Kattengat in Amsterdam. In 1991, Frank van Lamoen published a short biographical and bibliographical study in Dutch about this wealthy Amsterdam gentleman. Exactly what De Groot did remains unclear; city records list him as a schoolmaster. From his texts it appears that he travelled through Europe and exchanged ‘processes’ with apothecaries, alchemists and physicians along the way, but he did not attend a Dutch university, nor was he a member of the Amsterdam Collegium Medicum or are there indications that he ran an alchemical laboratory.
When Van Lamoen wrote his article, this Leiden manuscript was probably unknown (it was acquired by Leiden University at an auction in 2011), but it is interesting and remarkable for several reasons. First, it contains a number of recipes for medicinal preparations of gold, silver and zinc. Take for example a recipe for a medicinal gold powder, or ‘Cardilucius’ powder,’ probably taken from the work of seventeenth-century Nuremberg physician Johann Hiskia Cardilucius (1630–97). It involves dissolving gold in aqua regis, mixing it with rain water and precipitating it, resulting in a ‘purple powder’ that is useful in ‘malignant diseases.’ Although the idea that gold and gold preparations have medicinal qualities was quickly loosing credit among academically trained medical men in the eighteenth century, De Groot’s manuscript, which apart from Cardilucius’ powder lists four recipes for ‘Aurum potabile’ or drinkable gold, about which Tara Albert and I have written before, once more confirms there still was a strong popular belief in their effectiveness.
Another remarkable aspect this particular manuscript is that the handwriting is extremely neat and clear, suggesting the author intended it to be read, reproduced and understood by others – in contrast to many older alchemical manuscripts and printed texts. Although the descriptions of processes are still rather imprecise (i.e. in the recipe for Cardelucius’ powder the gold has to be dissolved in a ‘sufficient’ amount of aqua regis), there is no trace of the use of coded language and images so typical of much alchemical work. In fact, pure gold precipitate can be produced by dissolving gold in aqua regis (nitro-hydrochloric acid) and the result is indeed a powder – although a rusty orange rather than purple. Last but not least, De Groot’s manuscripts suggest the existence of a branch of an international network of alchemists and interested amateurs in the early eighteenth-century Netherlands who operated almost completely outside the Dutch academic world – a topic that certainly warrants further research.
 Van Lamoen, Frank, ‘Vijf Handschriften van Burghard de Groot M.D. (1661/62-1744)’, Jaarverslagen Koninklijk Oudheidkundig Genootschap, 1991, 73–82. In 2013 Van Lamoen wrote a blog post about the Arab pen-name Ali Puli, probably a pseudonym for De Groot.