The history of Ludovico Sicardi and the birth of geochemical

Ludovico Sicardi was a chemist and a pharmacist, and a passionate researcher, enthusiastic about phenomena related to volcanic activity. Due to a field survey within a project of mining research committed by a private company, he has the opportunity to visit the island of Vulcano (Eolie - Sicily), from December 1921 to June 1922. He was completely fascinated by the wild island of Vulcano and its gas manifestations. During several successive field trips in Vulcano, he observed and described the fumarolic field on a systematic basis, measuring the temperatures and recording their variations over time. He was one of the first to perform chemical analysis of fluids emitted by fumaroles in Vulcano Island and Solfatara di Pozzuoli (Italy). Furthermore, he was the first to suppose the coexistence of SO2 and H2S in fumarolic fluids, which by that time was considered to be impossible. Also, he succeeded in measuring their ratio by developing an in situ method that chemically separate the gaseous S-species. As the pioneer of applied geochemistry in volcanic fluids, he developed a method based on the sampling of fumarolic fluids using a glass flask that contained a NH4OH-AgNO3 solution to absorb the soluble acid gases (CO2, SO2 and HCl) and precipitate H2S as an insoluble Ag2S. A series of fortuitous coincidences allowed us to tell this story. Thanks to Prof. Marcello Carapezza and Prof. Mariano Valenza of the University of Palermo, the “scientific treasure” of Sicardi was preserved and it is nowadays studied and cataloged. It consists of Sicardi’s sampling-equipment, copies of the scientific articles, several historical maps and photos of Vulcano and Solfatara, manuscript notes and three important unpublished researches about Vulcano, Vesuvio and Campi Flegrei. Based on the remarkable scientific production, Sicardi has to be considered a precursor of modern volcanic monitoring based on fluid geochemistry.