Taken as a group, the articles illustrate development of the concepts of element and atom. The first set examine the idea of element from the pre-scientific four elements of the ancients to the empirical and provisional notion of elements as the ultimate products of chemical analysis. The next set concern the atom and the atomic-molecular theory proposed by Dalton and modified by Gay-Lussac and Avogadro. Next, attention returns to elements, and in particular to their classification: the law of octaves of Newlands, the periodic system of Mendeleev, and the admission into that system of the previously unsuspected noble gases. Finally (for the book at any rate), the last set of cases treat the realization that the atom has pieces and is not indivisible.
Of course, scientific understanding of atom and element did not stop evolving in 1913, the publication date of the last annotated paper in this collection. Quantum theory is crucial to a modern view of the structure of atoms and molecules, and a still deeper understanding of the nucleus is needed to explain what distinguishes one element from another and one isotope from another. But those are other stories.
The closest antecedents to the present work are the case histories in science described and advocated by James Bryant Conant [Conant 1957]. I embrace Conant's notion that the work of great scientists of the past can be used to illustrate the practice of science to educated people who are not familiar with the working of science. I maintain further that cases from the history of chemistry merit detailed study from students and teachers of chemistry as well, presenting an opportunity to learn some of the history of their field as well as how some of its great practitioners operated.
My approach differs from Conant's in format and organization. Each of the following chapters is built around words of an original researcher. A selection from the researcher's writings, whether the formal announcement of a discovery to the scientific community at the time or a later retrospective on previous work, stands in the foreground of each case. Each selection is also preceded by a brief introduction and followed by a list of references. Extensive commentary on each selection is presented in the form of footnotes. These notes explain terms, provide additional historical details, or draw attention to methodological or pedagogical points. The purpose of the notes is to facilitate the close reading of the original articles by different groups of readers with a variety of interests and background knowledge. I have also taken advantage of some of the opportunities the Internet offers. In addition to hyperlinks from chapter to chapter within this work, there are links to other papers posted at my Classic Chemistry website and John Park's ChemTeam site, links to glossary definitions at Classic Chemistry, and illustrations of protagonists from a variety of Internet sites.
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