This article examines the revisionist role that current debates and philosophical positions on extended cognition might play for the historian of science, and uses as its case study August Kekulé’s formulation of the benzene molecule’s structure, including the dreams that Kekulé reported as the origin of his model. It builds on the notion of engaging philosophical positions through the historiography of nineteenth-century chemistry, but also examines some of the implications of the history of science for extended cognition. While an extended (...) cognition approach to Kekulé’s use of graphics and visual materials is promising, I argue that there is less usefulness for the idea of collective cognition. Instead I advocate using detailed historical studies to test theories of extended cognition. (shrink)

This article attempts a contextual study of the origin and early development of August Kekulé's theory of aromatic compounds. The terminus a quo is essentially August Hofmann's coining of the modern chemical denotation of ‘aromatic’ in 1855; the terminus ad quem is the first full codification of Kekulé's theory in the sixth fascicle of his Lehrbuch der organischen Chemie, published in the summer of 1866. Kekulé's theory is viewed in context with the earlier and concurrent experimental work of such chemists (...) as Hermann Kolbe, Friedrich Beilstein, Rudolph Fittig, and Hugo Müller. The reception of the theory is briefly examined. Attention is paid to the role of Kekulé's molecular models and of his celebrated dream anecdote of the snake that seizes its own tail. The episode is used as a case study for the continuity of scientific progress, and to illustrate the close reciprocal interactions of hypothesis and experiment in the evolution of a scientific theory. (shrink)

A selective history of the benzene problem is presented, starting with August Kekulé's proposal of a hexagonal structure in 1865 and his hypothesis of 1872 that the carbon–carbon bonds oscillate between single and double. Only those theories are included that were accepted or at least discussed by a significant number of chemists. Special attention is given to predictions, their empirical tests, and the effect of the outcomes of those tests on the reception of the theories. At the end of the (...) period covered by this article, chemists generally accepted the valence bond theory proposed by Linus Pauling; some of them considered this a more sophisticated version of Kekulé's oscillation hypothesis. The sequel describes the replacement of the valence bond theory by the molecular orbital theory in the period ending around 1980. (shrink)

What is it that turns a new observation into a true scientific discovery? And who may claim the credit? Theoreticians of science, the foremost thinkers of their times among them, have tried to answer these fundamental questions about the nature of scientific progress and discovery. With clear insight and the chemical as well as philosophical wisdom gained from over fifty years as a practising chemist, Jerome Berson puts their theories to the test. The development of chemistry into a "modern" science (...) during the last two centuries provides him with ample cases to illustrate the way scientific progress really happens. Kekul?'s struggle to arrive at a structure for benzene, the paradigm change that was necessary to accept the reality of molecular rearrangements, and other episodes are retold here from the philosopher's as well as from the practitioner's perspective, shedding light on the way scientists think and act. Berson's account of the rather unphilosophical way in which scientific discoveries are made includes the realization that even a false hypothesis, such as Woodward's ideas about the biosynthesis of strychnine, may help rather than hinder scientific progress. Scientists of all ages, as well as many non-scientists, will find this a highly readable and unusual book. (shrink)

Chemical visualizations and models are special kinds of situated, inductive arguments. In this paper, I examine several historical case studies—an archive of images from museums, special collections, and popular magazines—as examples of emergent practices of physical modeling as theoretical play which became the basis for molecular biology and structural chemistry. Specifically, I trace a legacy of visualization tools that starts with Archibald Scott Cooper and Friedrich Kekulé in the late 1800s, crystallizes as material manipulatives in Kekulé’s student Jacobus Henricus Van’t (...) Hoff and his folded paper “toys,” is legitimized in the California lab of Linus Pauling, and is glorified in the popular imaginary with James Watson and Francis Crick’s model of DNA. My tracing then follows several threads into contemporary modeling practices. I ultimately argue that modeling play, originally outside of the boundary of deductive, positivist science, is now an accepted mode of inductive reasoning in these related chemical fields. (shrink)

I’ve just discovered that the Abstract painting has similarities not only with the micro-cosmos (as it is stated in the book “Man and His Symbol” by dr. CG Jung) but also, which is very astonishing, with the macro-Cosmos. Shortly, Hilma af Klint painted in her “The Ten Largest” symbols that are amazingly similar with modern astro-physics pictures that were made, many decades later, by the Hubble Telescope (and were not available for human eyes on the af Klint times). The research (...) aim is to prove that the human mind capacity for producing symbols with connection to the future science (see the known example of chemist August Kekule and the benzene formula) is bigger than it was thought. The research method is based on personal specific skills that are focused on deciphering scientifical and cultural symbols. Based on my technique that I developed in a couple of years, I managed to publish articles like “Fibonacci Numbers in Cucuteni Culture” on the “History Files” portal or “Mathematical equation, hidden in Brâncusi’s Triptych from Târgu-Jiu”. But my discovery about Hilma af Klint is the greatest. (shrink)

Organic chemistry provides fertile ground for scholars interested in understanding the role of non-linguistic representations in scientific thinking. In this discipline, it is not plausible to regard diagrams as simply heuristic aids for expressing or applying what is essentially a linguistic theory. Instead, it is more plausible to think of linguistic representation as supplementing theories whose principal expression is diagrammatic. Among the many sorts of diagrams employed by organic chemists, structural formulas are the most important. In this paper, by examining (...) two central episodes in the development of structural formulas—Kekulé’s proposal of a structure for benzene and Ingold’s explanation of dipole moments in terms of ‘mesomerism’—I investigate how the norms for the production and interpretation of structural formulas evolve in response to experimental results and theoretical developments. I conclude that one principal way in which structural formulas embody the theory of organic chemistry is through these evolving norms. (shrink)

The authors discuss Popper's and Kuhn's theories of science and consider whether these can explain the real course taken by the history of science, that is the real behaviour of scientists seen in an historical light. It has mainly to do with the problem of what criteria influence scientists in deciding on the acceptance of one of several possible theories. The authors postulate the necessity of introducing the category of "objective technological Erkenntnisinteresse" to help solve the problem. They illustrate this (...) by analysing the various models of the structure of Benzol, proposed by Kekulé, Claus and Ladenburg. According to the authors, Popper and Kuhn cannot explain the fact that the model of Kekulé was readily accepted. It can however be explained with the category of Erkenntnisinteresse. (shrink)

SummaryKekulé first suggested a hexagonal structure for benzene in 1865. For over a half-century after, chemists struggled to reconcile proposed structures for benzene and other aromatic compounds with their resistance to chemical transformation and tendency to maintain the type during reaction. The combined structural and reactivity features of these compounds were eventually covered by the term ‘aromaticity’. Kekulé, Bamberger and Thiele had each proposed a criterion for aromaticity; all were either empirically contradicted or incapable of evaluation. In the 1930s, two (...) rival quantum mechanical methods succeeded in establishing a physical basis for aromaticity. Using valence bond theory, Pauling attributed benzene's stability to its being a resonance hybrid of several Lewis structures. Calculating resonance energies was challenging but manipulating Lewis structures was not; that procedure provided qualitative insights into aromatic structure and reactivity. Resonance theory appealed especially to organic chemists and eclipsed Hückel's contemporaneous molecular orbital approach, which remained relatively inaccessible. In the 1950s, however, simple rules derived from Hückel's mathematics, combined with proton NMR data, provided seemingly universal criteria for aromaticity. In the event, post-1950 discoveries of non-organic, three-dimensional compounds such as ferrocene and the fullerenes that exhibit aromatic properties led chemists to doubt the utility and universality of ‘aromaticity’ as a concept. A recent consensus maintains that aromaticity is a multi-variable phenomenon that cannot be reduced to a strict definition, a property it shares with other core chemical concepts such as ‘acidity’ and ‘reactivity’. (shrink)

In these articles Professor Brooke has aimed to expose and explore the many layers of philosophical debate that accompanied the development of chemistry in the 100 years from Priestley to Kekulé. During this period the foundations of our modern science were laid: Lavosier's 'chemical revolution', Dalton's atomic theory, the electrochemical concepts of Berzelius transformed the science, as did new ideas of valency and molecular structure. But it was also a period of intense controversy when chemists called each other brigands and (...) assassins. (shrink)

Historically, the scientific method has been said to require proposing a theory, making a prediction of something not already known, testing the prediction, and giving up the theory (or substantially changing it) if it fails the test. A theory that leads to several successful predictions is more likely to be accepted than one that only explains what is already known but not understood. This process is widely treated as the conventional method of achieving scientific progress, and was used throughout the (...) twentieth century as the standard route to discovery and experimentation. But does science really work this way? In Making 20th Century Science, Stephen G. Brush discusses this question, as it relates to the development of science throughout the last century. Answering this question requires both a philosophically and historically scientific approach, and Brush blends the two in order to take a close look at how scientific methodology has developed. Several cases from the history of modern physical and biological science are examined, including Mendeleev's Periodic Law, Kekule's structure for benzene, the light-quantum hypothesis, quantum mechanics, chromosome theory, and natural selection. In general it is found that theories are accepted for a combination of successful predictions and better explanations of old facts. Making 20th Century Science is a large-scale historical look at the implementation of the scientific method, and how scientific theories come to be accepted. (shrink)

Christian Wilhelm Blomstrand, Professor of Chemistry and Mineralogy at Lund University from 1862 to 1895, was one of the important chemists of the second half of the nineteenth century. His theoretical ideas and experimental accomplishments contributed to advances in several branches of chemistry. Living in Sweden during a transitional period between the older and newer chemistry and being a scientific as well as a political conservative, Blomstrand sought to reconcile Berzelius's dualistic theory with the unitary and type theories. He was (...) opposed to Kekulé's dogma of constant valency, and he strove to establish a sound and complete theory of variable valency. This article briefly outlines Blomstrand's life and considers his best known book, Die Chemie der Jetztzeit , as well as his work on mineralogy, inorganic chemistry , and his theoretical views on valency, diazo compounds, and metal-ammines. His so-called ‘chain theory’, as developed and modified by his fellow Scandinavian chemist and close friend, Sophus Mads Jørgensen, was for more than three decades the most popular and successful of the numerous attempts to explain the constitution, properties, and reactions of coordination compounds. (shrink)

A selective history of the benzene problem is presented, starting with August Kekule's proposal of a hexagonal structure in 1865 and his hypothesis of 1872 that the carbon-carbon bonds oscillate between single and double. Only those theories are included that were accepted or at least discussed by a significant number of chemists. Special attention is given to predictions, their empirical tests, and the effect of the outcomes of those tests on the reception of the theories. At the end of the (...) period covered by this article, chemists generally accepted the valence bond (resonance) theory proposed by Linus Pauling; some of them considered this a more sophisticated version (and thus a vindication) of Kekule's oscillation hypothesis. The sequel (to be published in the following issue) describes the replacement of the valence bond theory by the molecular orbital theory in the period ending around 1980. (shrink)

In my previous article on the benzene problem, I described how Pauling's valence bond (resonance) theory, sometimes regarded as a modernized version of Kekule's oscillation hypothesis, came to be accepted by chemists by the end of World War II. But the alternative molecular orbital theory, proposed by Mulliken, had already been developed and was regarded as quantitatively superior by many quantum chemists, though it was not as easy to visualize and did not seem to harmonize as well with traditional chemical (...) concepts. During the 1950s and 1960s, thanks to the efforts of Charles Coulson and many other theorists, the molecular orbital approach not only dominated theoretical discussions but also started to be accepted by the chemical community as a whole and became the preferred description for benzene. Possible reasons were: its greater calculational convenience when applied to large molecules; better expository methods directed toward chemists; the spectacular success of the Woodward-Hoffmann rules for pericyclic reactions and Fukui's frontier orbital theory; and the development of a general theory of aromaticity, which predicted properties of similar molecules such as cyclobutadiene (C4H4). The relative importance of these reasons is explored through a mail survey of chemists. (shrink)

Because most chemical reactions, by definition, cannot avoid breaking of bonds, weakly bonded species exist fleetingly in almost every chemical change. Historically, chemical quantum mechanics was aimed at explaining the nature of strong bonds. The theory involved a number of approximations to the full solution of the Schrödinger equation. The study of non‐Kekulé molecules provides an opportunity to test whether modern quantum chemical computations are competent to deal with the nature of molecules with very weak bonds. †To contact the author, (...) please write to: Department of Chemistry, Yale University, New Haven, CT: 06520‐8107; e‐mail: [email protected]. (shrink)

Many theories require empirical patches or ad hoc assumptions to work properly in application to chemistry. Some examples include the Bohr quantum theory of atomic spectra, the Pauli exclusion principle, the Marcus theory of the rate-equilibrium correlation, Kekule’s hypothesis of bond oscillation in benzene, and the quantum calculation of reaction pathways. Often the proposed refinements do not grow out of the original theory but are devised and added ad hoc. This brings into question the goal of constructing theories derived from (...) first principles and the concept of ranking the merit of theories according to their freedom from empirical contamination. (shrink)

This chapter contains sections titled: * Notes * References.