Level: introductory
Reference: Stanislao Cannizzaro, "Sketch of a Course of Chemical Philosophy," Nuovo Cimento 7, 321-366 (1858)
Notes: Stanislao Cannizzaro's (1826-1910) outline of a course in chemical philosophy was instrumental in gaining acceptance of Avogadro's hypothesis and putting atomic weights on a common and reliable basis. This work reviewed the evidence for Avogadro's hypothesis and met the objections to the hypothesis that had held sway 50 years earlier. In the process, Cannizzaro clarified concepts of atom and molecule. This set the stage for gas density measurements to be used for molecular weight determinations (as Jean-Baptiste Dumas had done), removing some of the ambiguities about molecular formulas that had dogged determination of atomic weights since the time of Dalton. Cannizzaro also used the heat capacity law of Dulong & Petit to remove some ambiguities in the atomic weights of atoms not amenable to investigation through volatile compounds. (Classic Calculations includes exercises based on the work of Avogadro, Dalton, Dulong & Petit, and Dumas.)
This exercise draws on some data presented in Cannizzaro's outline as an example. Cannizzaro used these data rather differently, though. He was not trying to illustrate the law of multiple proportions, and he went on to bring in some heat capacity data on these compounds. Since Cannizzaro's paper helped establish reliable atomic weights, he could hardly draw upon a modern table of such weights as the exercise does in exercise 2.
Solutions: To download solutions, go to:
http://web.lemoyne.edu/giunta/classicalcs/cannizzaro.doc
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