The precious "scientific heritage" of Mariano Valenza: the unknown history of Ludovico Sicardi and the birth of the modern volcanology

Mariano Valenza was an important scientific figure of the geochemical community and a person characterized by his great intellect, diplomacy and human qualities. Sadly, he passed away in July of 2018, leaving a great void. He left us a precious treasure for all the geochemists involved in volcanology: the story and the memory of Ludovico Sicardi. Indeed, Valenza carefully preserved in his office, for a long time, four boxes containing the scientific material belonged to Ludovico Sicardi. As often happens, a little by chance, the precious material returned to light thirty-five years later, on the 20th of April 2018, and was donated to the Museum of Mineralogy of Palermo. It is nowadays subject of study and cataloging by the volunteers of the Associazione Naturalistica Geode. The “scientific treasure” consists of the personal field-equipment of Sicardi, glassware, copies of the scientific articles, many old maps of volcanic areas, several historical photos of Vulcano and Solfatara. Among all these findings, several manuscript notes and three important unpublished researches about Vulcano, Vesuvio and Campi Flegrei. Who was Ludovico Sicardi? Sicardi was a chemist and a pharmacist, who was passionate about volcanoes and, in particular, enraptured by the island of Vulcano (Eolie - Sicily). During his several field trips in Vulcano, he observed and described the fumarolic field on systematic basis, measuring the temperatures and recording their variations over time (Sicardi, 1973). He was the first to perform chemical analysis of fluids emitted by fumaroles in Vulcano Island and Solfatara. Furthermore, he was the former to suppose the coexistence of SO2 and H2S in fumarolic discharges, 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 S-gaseous species. This method was based on the sampling of fumarolic fluids using a glass flask that contained a NH4OHAgNO 3solution, with the aim to absorb the soluble acid gases (CO2, SO2 and HCl) and precipitate H2S as an insoluble Ag2S (Sicardi, 1955). Based on his remarkable scientific production, Sicardi can be considered as a precursor of the modern Volcanology and a pioneer of the volcanic monitoring techniques.We are extremely grateful to Mariano Valenza for giving us this fascinating story.