Stanislao Cannizzaro and his contribution to the development of modern chemistry.
I - Fisica nucleare e subnucleare
Aula GSSI Rettorato - Auditorium - Martedì 24 h 14:30 - 15:30
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Stanislao Cannizzaro major contribution to Chemistry was in the philosophical field, despite his remarkable experimental achievements (the syntheses of cyanamide and of benzylic alcohol). He developed a simple method to correctly determine the atomic weights of the elements, thus solving an age-old chemical problem. In his speech at the first International Chemistry Congress (Karlsruhe, 1860), he suggested that, as experimental evidence showed, gaseous elements consisted of molecules, instead of single atoms. According to Avogadro's law, molecular weights of gaseous substances could be obtained by matching their specific weight against a standard (gaseous hydrogen); then, from their per cent composition, the atomic weights of elements could be determined. The youngest Congress attendants (for instance, Mayer and Mendeleev) were strongly impressed by his arguments, which gave new impetus to their speculations. Thus, Mendeleev found the periodicity law, which organizes elements in a natural ordered pattern, known as Periodic Table. Cannizzaro's method helped also to clarify the concept of valence, and resolve chemical structures, giving a systematic theoretical asset to the quickly growing organic chemistry. Finally, several high-level chemists spread all over the Country, from the chemical Schools that Cannizzaro founded and led in Palermo and in Rome.