After 150 years of scientific developments, the periodic system of chemical elements is still an icon of modern science. Its resilience is striking. The icon used today by scientists and teachers is in fact the outcome of many rearrangements and reinterpretations by the scientific community during that period. This success is often explained as a result of the underlying atomic structure, discovered in the first decades of the 20th century, an explanation that completely neglects the fine structure of the process (...) of ongoing renegotiation and successive stabilizations. How did indeed contemporary scientists navigate in times of reinterpretation? The physicist Lise Meitner and the chemist Ida Noddack were, in different ways, involved in discoveries and interpretations of the periodic system. In 1934, as part of the celebration of the centenary of Dmitri Mendeleev's birth, they each published an article on the system: Meitner in Die Naturwissenschaften, and Noddack in Angewandte Chemie. These two articles, written from the perspectives of a nuclear physicist and a chemist experienced in searching for undiscovered elements, respectively, constitute excellent sources for understanding what new discoveries and insights meant for the meaning and value of the periodic system at the very beginning of the nuclear age in science. Through an analysis of the two contributions, we will argue that resilience is the foremost value of the periodic system. We will also discuss what this value means for the future of the periodic system and its representations. (shrink)

This article focuses on the Russian chemist Dmitri Ivanovich Mendeleev's assessment of certain representations of various aspects of the periodic system that employed more mathematical methodology. The equations of interest were created by E. J. Mills, B. N. Chicherin, and J. H. Vincent. The English chemist Mills tried to find a firmer numerical basis for the periodicity of the elements. The Russian lawyer and political philosopher Chicherin was convinced of the existence of a mathematical law underlying the periodic system. The (...) English physicist Vincent explored the connection between atomic weights and the elements' order in listings based on atomic weights—a project which he associated with the periodic system of elements. Although, for Mendeleev, the equations of Mills, Chicherin, and Vincent promised a more precise expression of the law of periodicity, he continued to invoke his earlier standards. In particular, Mendeleev wanted the equations to respect the individuality of the elements, and called for completeness in conveying the complexities of chemical phenomena. Thus, the very qualities that he had valued while developing his periodic system in 1869–1871 also characterised his evaluation of the new means of representing aspects of that system. (shrink)

Around fifteen years before the chemical substance alumina could be decomposed in the laboratory, it was identified as a compound and predicted to contain a new element called ‘aluminium’. Using this episode from early nineteenth-century chemistry as a case study for the use of analogical reasoning in science, this paper examines how chemists relied on chemical classifications for the prediction of aluminium. I argue that chemists supplemented direct evidence of chemical decomposition with analogical inferences in order to evaluate the composition (...) of substances. Since they were established on the basis of relevant similarities in chemical properties, classifications were taken to reflect so-called ‘chemical analogies’ between substances. In combination with the knowledge that analogous properties indicated similarities in composition, this enabled chemists to infer the composition of experimentally indecomposable substances by analogy. The trust in such analogical inferences, even if they could not be confirmed through experiment, was justified by pragmatic considerations. Whereas the possibility of decomposing a substance depended on the available laboratory techniques, chemical analogies were thought to last independently of internal composition. It was therefore more practical to keep well-established classes of substances together rather than separate them on the basis of experimental results that might evolve as new techniques were developed. Besides highlighting the links between analogical reasoning and classification, this paper also illustrates the importance of analogy in the evaluation of elementary nature in the early nineteenth century. (shrink)