In Renaissance alchemy, alkahest was the theorized "universal solvent". It was supposed to be capable of dissolving any other substance, including gold, without altering or destroying its fundamental components.
Among its philosophical and spiritual preoccupations, Hermeticism was more anciently concerned with the panacea, but (in the context of reformed understandings of human physiology) the emergent Latin alchemy associated with European humanism was itself transmuted into a new medical and pharmaceutical philosophy. The Swiss physician and alchemist Philippus Paracelsus (1493-1541), who gave his name to the early modern school of medical theory known as Paracelcism, first made mention of the alkahest as a chemical which could fortify the liver, and (in instances where the liver failed) could act as a substitute for its functions (see De Viribus Membrorum Spiritualium, Cap. VI, "De Cura Epatis", at p. 10). By reducing or dissolving substances into their fundamental virtues and properties, it was hoped to gain control of those invaluable medical healing properties (see also azoth), and for this reason the alkahest (also known as the ignis gehennae) was earnestly sought, and the reality (or otherwise) of its existence was debated among the alchemists and philosophers.
History
Alkahest became very popular in the 17th and 18th centuries through J.B. van Helmont, after which it was taken less seriously over time. Its prevalence in the 17th and 18th centuries, despite its otherwise absurd and extreme qualities, was likely due to the popularity of alchemy at the time and the lack of an adequate alternative theory of chemistry. Those who followed and trained under Paracelsus did not think of the alkahest as van Helmont did, but slowly built upon the ideas posed by their teacher. Tobias Ludwig Kohlhans (1624-1705) suggested in his dissertation of the spleen, that alkahest could be found in the lymphatic vessels of animals. This was then contested and doubted by Helmont, Henry Oldenburg (later in 1661), and Goddard, who raised questions about the lymph's "sweetly acidic" quality, the necessity of a hypothetical universal solvent to explain the acidity in empty animal lymphatic vessels, its ability to be generated within the body, and how it differed from that of the other fluids or humours in the body. The German alchemist Johann Kunckel (1630-1703) and others in time began to see the alkahest as merely fantasy and wishful thinking. Ladislaus Reti, a 20th-century historian of science, investigated alchemical recipes involving alkahest and found that no chemical was sufficient in breaking down the wide variety of materials Helmont supposed. Reti points out that in such recipes, an alcohol solution of potassium hydroxide could have been used instead.
Etymology
There is no consensus on the origin and etymology of the word alkahest, as Paracelsus left no trace or history of the word. George Starkey argued it came from the German word al-gehest (all spirit). Johann Rudolph Glauber posed that it could have come from the words alhali est, the German word al gar heis, or Al zu hees, meaning "very hot". Cleidophorus Mystagogus in England argued for its root being of Belgian or High Dutch. Paracelsus believed that alkahest was, in fact, the philosopher's stone, whereas Henry Oldenburg in 1661 made experimental connections between the legendary alkahest, and the liquid discovered in the lymphatic vessels of animals introduced by Kohlhans. Boerhaave in his textbook Elementa Chymiae (1732), did not think Alkahest was the philosopher's stone but that it was in fact of greater importance and value than the stone.
Other names
Helmont considered the alkahest to have never-ending reusability, calling it an "immortal". He also used the term "maccabean fire" because of its similarities to the "thick water" in the deuterocanonical Book of Maccabees in the Old Testament. Another name for the Alkahest termed by Helmont was ignis gehennae. Other names include Latex (or "clear water reduced to its minutest atoms"), and primum Ens Salum (or "salt exalted to its highest degree").