Читать книгу The Fontana History of Chemistry - William Brock J. - Страница 7

That all plants immediately and substantially stem from the element water alone I have learnt from the following experiment. I took an earthern vessel in which I placed two hundred pounds of earth dried in an oven, and watered with rain water. I planted in it the stem of a willow tree weighing five pounds. Five years later it had developed a tree weighing one hundred and sixty-nine pounds and about three ounces. Nothing but rain (or distilled water) had been added. The large vessel was placed in earth and covered by an iron lid with a tin-surface that was pierced with many holes. I have not weighed the leaves that came off in the four autumn seasons. Finally I dried the earth in the vessel again and found the same two hundred pounds of it diminished by about two ounces. Hence one hundred and sixty-four pounds of wood, bark and roots had come up from water alone.

(JOAN-BAPTISTA VAN HELMONT, 1648)

Helmont’s arresting experiment and conclusion capture the essence of the problem of chemical change. How and why do water and air ‘become’ the material of a tree – or, if that sounds too biochemical, how and why do hydrogen and oxygen become water? How does brute matter assume an ordered and often symmetrical solid form in the non-living world? Helmont’s experiment also raises the issue of the balance between qualitative and quantitative reasoning in the history of chemistry. Helmont’s observations are impeccably quantitative and yet, because he ignored the possible role of air in the reaction he was studying, and since he knew nothing of the hidden variables of nutrients dissolved in the water or of the role of the sun in providing the energy of photosynthesis, his reasoning was to prove qualitatively fallacious.

Chemistry is best defined as the science that deals with the properties and reactions of different kinds of matter. Historically, it arose from a constellation of interests: the empirically based technologies of early metallurgists, brewers, dyers, tanners, calciners and pharmacists; the speculative Greek philosophers’ concern whether brute matter was invariant or transformable; the alchemists’ real or symbolic attempts to achieve the transmutation of base metals into gold; and the iatrochemists’ interest in the chemistry and pathology of animal and human functions. Partly because of the sheer complexity of chemical phenomena, the absence of criteria and standards of purity, and uncertainty over the definition and identification of elements (the building blocks of the chemical tree), but above all because of the lack of a concept of the gaseous state of matter, chemistry remained a rambling, puzzling and chaotic area of natural philosophy until the middle of the eighteenth century. The development of gas chemistry after 1740 gave the subject fresh empirical and conceptual foundations, which permitted explanations of reactions in terms of atoms and elements to be given.

Using inorganic, or mineral, chemistry as its paradigm, nineteenth-century chemists created organic chemistry, from which emerged the fruitful ideas of valency and structure; while the advent of the periodic law in the 1870s finally provided chemists with a comprehensive classificatory system of elements and a logical, non-historically based method for teaching the subject. By the 1880s, physics and chemistry were drawing closer together in the sub-discipline of physical chemistry. Finally, the discovery of the electron in 1897 enabled twentieth-century chemists to solve the fundamental problems of chemical affinity and reactivity, and to address the issue of reaction mechanisms – to the profit of the better understanding of synthetic pathways and the expansion of the chemical and pharmaceutical industries.

Returning to Helmont’s tree, an arboreal image and metaphor can be usefully deployed. The historical roots of chemistry were many, but produced no sturdy growth until the eighteenth century. In this healthy state, branching into the sub-disciplines of inorganic, organic and physical chemistry occurred during the nineteenth century, with further, more complex branching in the twentieth century as instrumental techniques of analysis became ever more sophisticated and powerful. Growth was, however, dependent upon social and environmental conditions that either nurtured or withered particular theories and experimental techniques.

Although conceived as a work of synthesis for the 1990s (there has been no extensive one-volume history of chemistry published since that of Aaron Ihde in 1964), The Fontana History of Chemistry draws extensively upon some of the themes and personalities treated in my own research as well as upon the post-war work of other historians of chemistry. Gone are the days of Kopp and Partington, when a history of chemistry could be allowed to unfold slowly in four magisterial and detailed volumes. My volume is designed to be neither a complete nor a detailed narrative; nor is it a work of reference like James R. Partington’s History of Chemistry, to which I, like all historians of chemistry, remain profoundly indebted. I am particularly conscious, for example, of ignoring developments such as photography (that most chemical of nineteenth-century arts), spectroscopy, Russian chemistry, or the emergence of ideas concerning atomic structure. In some cases, as with the omission of any emphasis on the role of Avogadro’s hypothesis in the nineteenth-century determination of atomic and molecular weights, the lacuna is justified historiographically; in other cases, as with my muted references to the roles of rhetoric and language in chemistry, it was a decision not to introduce a contemporary historiographic fashion in a book largely dedicated to a readership of chemists and science students.

In yet other cases, choices of subject matter, and therefore of omission, have stemmed from the decision to structure chapters around seminal texts, their writers and the schools of chemists associated with them. This principle of organization has been freely borrowed from Derek Gjertsen’s The Classics of Science (New York: Lilian Barber, 1984) and a book edited by Jack Meadows, The History of Scientific Development (Oxford: Phaidon, 1987), with which I was associated. To use a metaphor from organic chemistry, the book is arranged around textual types, each title standing symbolically for a paradigm, a theoretical, instrumental or organizational change or development that seems significant to the historian of chemistry. I have tried to lay equal emphasis upon the practical (analytical) nature of past chemistry as much as on its theoretical content, and, although it would have taken a volume in itself to analyse the development of industrial chemistry, I have tried to provide the reader with an inkling of the application of chemistry. Wherever possible I have stressed the significance of chemistry for the development of other areas of science, and I have noted some of the false steps and blind alleys of past chemistry as much as the developments that still remain part of the scientific record. Echoing Ihde’s incisive treatment, The Fontana History of Chemistry also provides a generous treatment of twentieth-century chemistry – albeit within the constraints of my chosen themes and typologies. I have tried wherever possible to illustrate the international nature of the chemical enterprise since the seventeenth century.

Helmont’s tree leads us both backwards and forwards in time – forwards to when evidence accrued that air (and gases) did participate in chemical change, and backwards to the ancient traditions of elements and of transmutation that Helmut had inherited. The book opens with the roots of chemistry and the social, economic and religious environments that promoted it before the time of Helmont. In particular, the opening chapter examines early chemical technologies and their rationalization by Greek philosophers in theories of elements or, more iconoclastically, in terms of corpuscules and atoms. The tree enters here again, for one of the perennial proofs for the existence of elements and for their number was the destructive distillation of wood by fire – an important phenomenon empirically (for it was the model for distillation techniques generally) and cognitively because it was the basis of the concepts of analysis and synthesis. Chemistry was, and is, concerned with the analysis of substances into their elements and the synthesis of substances from their elements or immediate principles.

The possibility of manipulating elementary matter into substances of commercial or – at the extreme – of spiritually uplifting value, such as silver and gold or an elixir of life, led to alchemy. The latter’s origin, as well as its formal connections with chemistry, are complex and even contentious. However, our contemporary demand for science to have empirical validation, as well as our respect for the technological manipulation of Nature’s resources for the benefit of humankind, can be traced back to the philosophical spirit of enquiry that underpinned alchemical investigations. And it goes without saying that alchemy provided early chemistry with much of its apparatus and manipulative techniques, as well as the idea of a formal symbolic language for practitioners of the art.

Each of the sciences, no doubt, has its own difficulties and peculiarities when it comes to presenting its historical development to a diverse audience of professional historians, scientists, students and laypersons; but chemistry, like mathematics, possesses a particularly intimidating obstacle in its language and symbolism, which potentially obscures what are usually quite simple theoretical ideas and experimental techniques. As William Crookes noted in 1865 when reviewing a book on stuttering that had been inappropriately sent to Chemical News for review:

Chemists do not usually stutter. It would be very awkward if they did, seeing that they have at times to get out such words as methylethylamylophenylium.

However, if (as Peter Morris has noted) the historian avoids chemical detail and language, the scientific story become exigious and almost trivial. For this reason, while the first twelve chapters should present little difficulty to a sophisticated general reader, I have not hesitated to use technical language in the five chapters that are devoted to twentieth-century chemistry. Because this is a history, and not a textbook, of chemistry, I have not defined and explained symbols, equations and technical vocabulary. These chapters will present little difficulty to readers who have a secondary or high-school foundation in chemistry (and will have the privilege of being critical of my treatment). At the same time, it is to be hoped that there is sufficient of a human interest story in the intellectual and experimental worlds of Pauling, Ingold, Nyholm, Woodward and the other giants of twentieth-century chemistry, to propel the non-chemical reader towards the final pages.

The history of chemistry has served and continues to serve many purposes: didactic and pedagogic, professional and defensive, patriotic and nationalistic, liberalizing and humanizing. As I write, especially in America, where words like ‘chemical’, ‘synthetic’ and ‘additive’ have unfortunately become associated with the pollution, poisoning and disasters caused by humans, the history of chemistry has come to be seen by leaders of chemical industry and educators as a possible way of revaluing chemical currency: that is, of demonstrating not only the ways in which chemistry plays a fundamental role in nature and our understanding of cosmic processes, but also how it is essential to the economy of twentieth-century societies. In other words, the history of chemistry not only informs us about our great chemical heritage, but justifies the future of chemistry itself. Such a justification echoes the liberal and moving words of the first major historian of chemistry, Hermann Kopp¹:

The alchemists of past centuries tried hard to make the elixir of life … These efforts were in vain; it is not in our power to obtain the experiences and views of the future by prolonging our lives forward in this direction. However, it is possible and in a certain way to prolong our lives backwards, by acquiring the experiences of those who existed before us and by learning to know their views as if we were their contemporaries. The means for doing this is also an elixir of life.

It is in this spirit that The Fontana History of Chemistry has been written.