Level: introductory
References: William Prout, "On the Relation between the Specific Gravities of Bodies in their Gaseous State and the Weights of their Atoms," Annals of Philosophy 6, 321-30 (1815); "Correction of a Mistake in the Essay on the Relation between the Specific Gravities of Bodies in their Gaseous State and the Weights of their Atoms," Annals of Philosophy 7, 111-3 (1816): both published anonymously.
Notes: William Prout (1785-1850) was a medical doctor with a great interest in chemistry. He developed analytical instruments and published chemical analyses of organic material. His analyses of food classified components which correspond essentially to proteins, carbohydrates, and fats. Prout was also recognized as a clinical authority on urinary and digestive disease.
By the end of the 19th century, however, Prout was best known for the hypothesis that atomic weights were multiples of that of hydrogen and the speculation that hydrogen was a fundamental building block of matter. These ideas were tremendously influential. They inspired ever more accurate determinations of atomic weights to test the multiples hypothesis. One of those sets of determinations, Lord Rayleigh's measurements of gas densities in the late 19th century, even led to the discovery of a new element (argon). As it became clear that the original multiples hypothesis was contradicted by experiment, various researchers modified rather than discarded it. In other words, even though the hypothesis suggested by Prout was not correct, it was too attractive to be regarded as entirely baseless. And indeed, there was something to the idea of simple building blocks of atoms after all: practically all the mass of atoms is in their nuclei, which are made of protons and neutrons, building blocks of nearly identical mass (one of which happens to be the nucleus of the dominant isotope of hydrogen). Prout's hypothesis is the subject of another set of exercises.
Solutions: To download solutions, go to:
http://web.lemoyne.edu/giunta/classicalcs/proutdens.doc
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