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Date and Place of birth: Palermo, Sicily, Italy (13-Jul-1826)
Date and Place of Death: Rome, Italy (10-May-1910)
Institutions (colleges and universities) where the scientist worked and studied: He entered the university of his native place with the intention of making medicine his profession, but he soon turned to the study of chemistry, and in 1845-46 acted as assistant to Rafaelle Piria (1815-1865), known for his work on salicin, who was then professor of chemistry at Pisa and subsequently occupied the same position at Turin. In 1851, he was made professor of chemistry and physics at Alessandria (in Piedmont), part of the Savoys’ pre-unification kingdom.
Major scientific contributions: During the Sicilian revolution he served as an artillery officer at Messina and was also chosen deputy for Francavilla in the Sicilian parliament; and after the fall of Messina in September 1848 he was stationed at Taormina. Cannizzaro established values for atomic and molecular weights, incidentally distinguishing the two, designating the weight of hydrogen as the universal standard by which other elements should be measured. He demonstrated that vapor densities could be applied in determining atomic and molecular weights. This was remarkable work, and the periodic table of elements (formulated later) owes much to Cannizzaro's efforts. Moreover, the recognition of universal constants destroyed the prevailing concept that organic and inorganic chemistry functioned under differing principles. Today, it seems incredible that atoms (and elements) were not clearly distinguished from molecules (and compounds), but while others had postulated this theory long before Cannizzaro, he was one of the first to propose a new order based on a practical rule; this was soon embraced internationally. In those days, the distinctions between the sciences of chemistry and physics were not always clearly expressed; as a distinct field of academic study (though often coinciding with chemistry), physics really evolved in the last decades of the nineteenth century. By today's standards, Cannizzaro might be considered a "chemical physicist."
Scientists who worked with him or her: In 1860, Cannizzaro actively supported the unification movement, and Garibaldi's revolt, in Sicily. He served briefly in the new Sicilian government, and helped to expand the chemistry department of the University of Palermo, where he remained until 1871. During the 1860s, he saw another series of bloody revolts --this time against the new government-- suppressed by northern Italian troops, but this failed to influence his strong loyalties to the unitary Italian state. Ever a political idealist, Cannizzaro accepted an appointment as senator in 1871 (when Savoyard forces occupied Papal Rome) and moved to Rome.