Level: introductory
Reference: William Hyde Wollaston, "A Synoptic Scale of Chemical Equivalents," Philosophical Transactions of the Royal Society 104, 1-22 (1814).
Notes: William Hyde Wollaston (1766-1828) was an important contributer to the study of chemical composition in the early 19th century. His analyses of acid salts provided examples of the law of multiple proportions. He also discovered the elements palladium and rhodium.
In late 1813 he read a paper that included an extensive compilation of "equivalent weights" or combining masses (closely related to molar masses) and a sort of chemical slide rule on which the weights were arranged. Wollaston's paper included not only a table of equivalent weights but a summary of data from which he compiled the table, mainly analyses published by other chemists. This exercise uses some of that data. It refers students to the periodic table for modern atomic masses, so the computation is not what Wollaston did with the data. In fact, Wollaston's calculations were conceptually similar to the ones required here, but in reverse: he knew or assumed the formulas for these materials and derived the equivalent weight (related to the atomic weight) of one of the components. For example, from the analytical data, the formula for litharge, and the equivalent weight of oxygen, he computed the equivalent weight of lead; etc.
Further information: A detailed summary of key primary literature on multiple proportions, the atomic hypothesis, and atomic weights, including some quantitative treatment of data may be found in Leonard Nash, "The Atomic-Molecular Theory," in James Bryant Conant, ed., Harvard Case Histories in Experimental Science, vol. 1 (Cambridge, MA: Harvard, 1957), pp. 215-321.
Solutions: To download solutions, go to:
http://web.lemoyne.edu/giunta/classicalcs/wollaston.doc
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