 He taught, for a short time, at Łódź but moved to Florence, Italy in 1925 to teach Rabbinical literature and the Talmud at the Rabbinic College there, the "Collegio Rabbinico".Apart from teaching he also engaged in research into the Jewish history in Italy.In the mid-1930s Sonne became the first to compile a partial catalogue of the "Biblioteca della Comunità Israelitica", looted by the Nazis in October 1943 and never recovered.