How Did the Tree of Knowledge Get Its Blossom? The Rise of Physical and Theoretical Chemistry, with an Eye on Berlin and Leipzig
2016; Wiley; Volume: 55; Issue: 18 Linguagem: Inglês
10.1002/anie.201509260
ISSN1521-3773
Autores Tópico(s)Philosophy and History of Science
Resumo“Physical chemistry is not just a branch on but the blossom of the tree of knowledge,” declared Ostwald, a most vocal advocate of his field, conceived as the basis for all of chemistry. This Essay describes the historical development of physical and theoretical chemistry with a focus on Berlin and Leipzig, its foremost centers in Germany. Physical and theoretical chemistry came about with a purpose, namely to save chemistry from becoming a collection of little disconnected facts. Its founders, Jacobus van't Hoff, Wilhelm Ostwald, and Svante Arrhenius, set out, at the end of the 19th century, to seek the general rather than cherish the particular by focusing on the processes of forming chemical compounds—that is on chemical reactions—rather than on the compounds themselves. They co-opted the methods of physics, especially thermodynamics, and their effort gave rise to the fields of physical and theoretical chemistry, which were here to stay and become a part of any chemistry of the future. The success of physical and theoretical chemistry in providing a common ground for chemistry was celebrated by Ostwald in his proclamation, “Physical chemistry is not just a branch on but the blossom of the tree of knowledge.” The fragrance of this blossom proved irresistible to scores of scientists who would lead chemistry through the quantum revolution and beyond, and find a new gratification in the premise that the road to general chemistry goes through physics and mathematics. Herein, I provide a tour along the timeline of the developments of physical and theoretical chemistry from its dawn in the 17th century to its triumphs during the post-quantum revolution era, up to about 1940, with an eye on the developments in Berlin and Leipzig. Chemistry as a science came about in a long process with only few revolutionary moments. Perhaps one such moment was the publication of Robert Boyle's book, The Sceptical Chymist, in 1661. In it, Boyle attempted to liberate chemistry from the grip of the “vulgar chymists” (as he called them), who were concerned with commerce and medicine, and make chemistry into a tool for the study of the workings of nature.1 Wielding skepticism against the Aristotelian elements and Paracelsian principles, Boyle strived to elevate chemistry to the status of a fundamental experimental science. His outlook is well captured by the statement:2 “I look upon experimental truths as matters of great concernment [importance] to mankind.” In keeping with this outlook, Boyle carried out countless experiments. Some were of general, enduring value. The inverse relationship between the pressure and volume of gases, known as Boyle's law, is perhaps the best example. He discovered it with a “pneumatic engine” built by his assistant Robert Hook (Figure 1). Boyle's law smacks of physics and mathematics—the other tools for understanding nature, which would prove to be not only interrelated but inseparable from each other and from chemistry. Timeline of the developments in physical chemistry during its dawn period 1650–1840. See text. The term physical chemistry appeared for the first time in the work of the Russian polymath Mikhail Lomonosov. Here is his definition (1752):3 “Physical chemistry is the science that must explain under provisions of physical experiments the reason for what is happening in complex bodies through chemical operations.” This definition sounds quite modern. However, it took more than a hundred years to become widely accepted as such. One of the first feats of chemistry that bore on all of science was the establishment of the law of the conservation of mass. Although its ur-form can be found already in the work of Lomonosov, it was put on a firm footing by the accurate experiments of Antoine Lavoisier and his wife, Marie-Anne, shown in Figure 1 in a double portrait by Jacque Louis David. Apart from being a scientist, Marie-Anne was also an artist, as alluded to by the folio seen in the background. Her artistic training was provided by David himself.1 The faith in the ability of physics and mathematics to aid in explaining chemical phenomena is reflected in this musing of Lavoisier's found in his correspondence with Pierre-Simon Laplace (1782):4 “Perhaps … some day … the mathematician will be able to calculate at his desk the outcome of any chemical combination, in the same way … as he calculates the motions of celestial bodies.” This sounds like a manifesto of theoretical chemistry: calculate in order to predict. In his 1789 masterpiece Traité élémentaire de chimie (Elements of Chemistry) illustrated by Marie-Anne, Lavoisier provided a list of 33 chemical elements that included light and caloric, the latter as the element of heat. Lavoisier's list signified a definitive departure from the Aristotelian—or prescientific—view of matter. The law of constant proportions, discovered by Joseph Proust,5 espoused Lavoisier's chemical elements and established the notion of a chemical compound as a combination of chemical elements in a particular ratio of integral amounts. When Joseph Gay-Lussac subsequently discovered the law of constant proportions for gases, he was smitten with it to the point that he declared:6 “We are perhaps not far removed from the time when we shall be able to submit the bulk of chemical phenomena to calculation.” A further step in elucidating the nature of matter was taken by John Dalton. In his work A New System of Chemical Philosophy, published in 1808, Dalton identified chemical elements with atoms—which he characterized as indivisible and indestructible particles that preserve their identities in chemical reactions. What added weight to Dalton's argument was that he declared atoms to have, well, weight, and proceeded to infer it from the law of multiple proportions, stoichiometry, etc. A major influence on Dalton was Isaac Newton, who in his mechanical derivation of Boyle's law7 assumed the existence of small particles (interacting via repulsive forces inversely proportional to their distance) but fell short of calling them atoms. Newton may have sought to avoid the stigma of atheism, which in his day was still attached to the atomistic views of Epicurus and Lucretius.8 However, Dalton was fearless and eloquent, as attested by his statement:9 “We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, [than] to create or destroy a particle of [say] hydrogen.” A table of 49 chemical elements ordered according to their atomic weights was drawn up by Jöns Jacob Berzelius in 1818.10 Berzelius, who enriched chemistry with many modern terms and discovered a number of chemical elements, also came up with the notion of isomer11 for what was discovered by his pupil Friedrich Wöhler (silver cyanate) and by Justus von Liebig (silver fulminate, an explosive). Wöhler, together with his friend Liebig, were engaged in a systematic study of mainly organic compounds within the framework of the above-mentioned chemical laws. The discovery of isomerism helped to cement the status of atomic theory in chemistry and foreshadowed the work of Alexander Butlerov, Emil Fischer, and others on chemical structure. Robert Boyle's goal to elevate chemistry to the status of a fundamental science was taken up during the last third of the 19th century by a trio of chemists who would become the founders of physical chemistry proper: Jacobus van't Hoff, Wilhelm Ostwald, and Svante Arrhenius. Trained primarily as organic chemists but with a predilection for physics and mathematics, they shared two pivotal views: Firstly, that chemistry was in need of a reform as it was drifting towards taxonomy—a collection of disconnected little facts bred mainly by organic chemists. Secondly, that chemistry should, like physics, speak the language of mathematics and seek the general rather than relish the particular. Key moments of the effort that ensued are captured in the timeline of Figure 2.2 Timeline of the key conceptual (on the left) and institutional (on the right) developments in physical and theoretical chemistry during the period 1845–1940. See text. The term “physical chemistry” that could—and would—be used for the chemistry of the future was, as we know, already in existence although not in circulation. However, some of the pioneers of physical chemistry preferred, at least for a while, the terms “general” or “theoretical” chemistry. But how does one seek the general in chemistry? To the trio, which would eventually become a triumvirate, the answer was: by focusing on the processes of forming chemical compounds—that is on chemical reactions—rather than by studying the compounds themselves. The pioneering paper on the key characteristic of a chemical reaction, the equilibrium constant, was published by two Norwegians, Cato Guldberg and Peter Waage, in Norwegian.12 The law they discovered, known as the law of mass action, remained well hidden until Ostwald finally came across it a dozen years later. According to Guldberg and Waage, the equilibrium state was the result of a balancing act between the forward and reverse reaction forces, characterized by chemical affinities. Ostwald corroborated the validity of the law by his own experiments and made it, along with the notion of chemical affinity, into a mainstay of his future work. Van't Hoff, who was among the first to apply thermodynamics to chemical problems, discovered the law independently and derived a formula that describes the temperature dependence of the equilibrium constant.13 Van't Hoff's work on the temperature dependence inspired Arrhenius to propose a relationship between the reaction rate and temperature—and to introduce the key notion of activation energy on the way.14 In addition, Arrhenius applied the theory of chemical equilibrium to electrolytes,15 which, from then on, would become one of the triumvirate's chief preoccupations and earn them the label “Ionists.” During the formative years of physical chemistry, the notion of chemical affinity underwent an overhaul—from its vague beginnings as a “chemical force” to being equated with the concept of free energy as developed by Herrmann von Helmholtz.16 The attempt of the Ionists to elevate chemistry as a science largely relied on applying the methods of thermodynamics to chemical processes. They spoke of “chemical dynamics,” a term later replaced by “thermochemistry.” “Chemical dynamics” still appears in van't Hoff's Nobel citation from 1901. In Nernst's citation, from 1920, it is already “thermochemistry.” During the same period, the thermodynamic work of Josiah Willard Gibbs, later characterized as the “principia of thermodynamics”, was blissfully ignored by chemists (including the Ionists), although it had answered all the questions that the chemists were asking—from chemical forces to the nature of the electromotive force.17 The reason was that Gibbs worked in splendid isolation in rural Connecticut and communicated with his European colleagues—mainly physicists—by mailing them reprints of his papers.18 He had to, as these appeared in the then (and now) obscure Transactions of the Connecticut Academy. In 1892, Ostwald translated Gibbs’ magnum opus into German.19 James Clerk Maxwell was among the most appreciative recipients of Gibbs's reprints. He was fascinated by Gibbs's work to the point that he sculpted, out of clay and plaster, a Gibbs energy surface as a function of volume and entropy for a water-like substance and traced the isotherms and isobars on the surface. Apparently Gibbs was quite pleased when the famous Maxwell sent him—a “chemical engineer from Connecticut”—a copy of the sculpture. Maxwell also shared with Gibbs a predilection for statistical methods in physics. Maxwell's velocity distribution anticipated Gibbs's work in that area and inspired Ludwig Boltzmann. Here's what Gibbs said about the benefits of statistical methods:20 “We avoid the gravest difficulties when … we pursue statistical inquiries as a branch of … mechanics.”3 Let me now briefly outline the institutional framework of physical chemistry. The first research university—based on the Humboldtian principle of the unity of teaching and research—was the Berlin University, founded in 1810 (and named only in 1949, during the political skirmishes in divided Berlin, after the Humboldt brothers).21 However, it wasn't the Berlin University that established the first research laboratory for chemistry, but rather Justus von Liebig's operation at the University of Gießen, in the 1820s.22 Liebig's school combined a well-equipped laboratory with a body of students enlisted in active, creative research. Liebig's school became a widely adopted model throughout Germany's roughly 30 universities (including 10 technical colleges). As a result, by the mid-19th century, German universities played a pace-setting role in chemical research worldwide.234 The first university to establish a chair in physical chemistry was Leipzig University. Its recipient was Wilhelm Ostwald, who would become a most vocal advocate of his field and founder of a highly influential international school of physical chemistry. Ostwald would also co-found, with van't Hoff, a tribune of the chemistry of the future, namely Zeitschrift für Physikalische Chemie, with an international editorial board. In his introduction to the first issue of the journal,24 Ostwald declared that “Physical Chemistry is not just a branch on but the blossom of the tree [of knowledge].”5 6 7 More chairs in physical chemistry quickly followed: for Hans Landolt in Berlin and Ostwald's pupils Walther Nernst and Arthur Noyes in Göttingen and at the Massachusetts Institute of Technology (MIT), respectively. By 1910, about a half of the German universities had a chair or section of physical chemistry.22 This reflected the view that physical chemistry was not just a core discipline of chemistry but also the basis of chemical technology. In contrast, Oxford and Cambridge established their chairs in physical chemistry only after World War I. The first journal outside of Germany dedicated to the new field was the Journal of Physical Chemistry (JPC), edited by Ostwald's pupil Wilder Bancroft. During its first decade JPC published 300 research papers, written almost entirely by Americans and Canadians. One quarter of these were Ostwald's pupils, among them Gilbert Newton Lewis, Arthur Noyes, and Theodore Richards. American physical chemists published in the Journal of the American Chemical Society (JACS) as well—and by 1926, over a quarter of all papers published by JACS were in physical chemistry. As a witness observed:22 “Physical chemistry now seems about to swallow up chemistry proper.” And what will, in turn, swallow up physical chemistry? Well, arguably, in all but name, chemical physics and theoretical chemistry. But in order to get there, we must gloss over the quantum revolution first. As Helge Kragh noted,25 “Quantum theory owes its origin to the study of thermal radiation, in particular to the ‘black-body’ radiation that Robert Kirchhoff had first defined in 1859–1860.” The experimental investigation of black-body radiation is a legacy of Helmholtz and his leadership at the Physikalisch-Technische Reichsanstalt (PTR). The discovery of the black-body radiation law by Max Planck,26 signified—in the words of Abraham Pais27—the first “coming” of Planck's constant. Three more comings of Planck's constant were needed in order for quantum mechanics to emerge: The second coming was in Einstein's paper on the light quanta28 (often incorrectly referred to as the photoeffect paper) and the third in his paper on the heat capacity of solids.29 This paper caught the eye of Walther Nernst, who saw in it a clue to his Heat Theorem. In response, Nernst co-organized the first Solvay conference. The fourth coming was in Bohr's model of the atom,30 which combined the extant quantum ideas with the discoveries of the electron and of the atomic nucleus.8 9 The discovery of quantum mechanics by Werner Heisenberg, Erwin Schrödinger, and Paul Dirac was surrounded by a host of other discoveries relevant to physical and theoretical chemistry. Among them was Einstein's analysis of Brownian motion31 and its experimental validation by Jean Perrin.32 This led to the definitive recognition of the particulate or atomic structure of matter—even by diehard physicists (with the exception of Ernst Mach) and physical chemists (including Ostwald). It also helped to precipitate the demise of the theory that proteins and other macromolecules were colloids. Max von Laue's discovery of X-ray diffraction by crystals33 had repercussions for the study of structure and the understanding of strong electrolytes—both key preoccupations of physical chemistry at the time and beyond. William Lawrence and William Henry Bragg's discovery of a law governing X-ray diffraction provided a key to the analysis of crystal structures.34 The work of Gilbert Newton Lewis35 and Irving Langmuir36 foreshadowed the theory of the covalent bond as due to a shared electron pair. The discovery of space quantization of angular momentum37 and of spin38 led eventually to NMR spectroscopy and other marvels of quantum science. On the heels of Schrödinger's wave mechanics came Friedrich Hund's discovery of tunneling.39 Moreover, the Pauli principle and Hund's rules—along with adjusted hydrogenic energy levels—proved capable of making sense of Mendeleev's periodic system of the elements.40 By deploying group theory across quantum mechanics, Eugene Wigner recast selection rules as the observable signature of an underlying physical symmetry.41 The Fifth Solvay conference, in 1927, consolidated quantum theory. When the dust of the quantum revolution settled, Dirac famously stated that:42 “The underlying physical laws necessary for the mathematical theory of … the whole of Chemistry are thus completely known, and the difficulty lies only in the fact that application of these laws leads to equations that are too complex to be solved.” So the key question of theoretical chemistry became: How can these these equations be solved? The quite astounding flurry of activity that ensued provided some answers. The 1927 paper by Walter Heitler and Fritz London on the homo-polar bond launched quantum chemistry.43 Apart from demonstrating that chemical bonding owes its existence to a quantum effect, Heitler and London provided the first example of the fine art of approximation that would be in such high demand in quantum chemistry. This paper was quickly followed by the introduction of the Born–Oppenheimer approximation,44 the consequential Thomas–Fermi model,45, 46 and Hartree's method of self-consistent field.47 The year 1931 can be, for good reason, characterized as the annus mirabilis of theoretical chemistry.48 The recasting by Fritz London,49 Henry Eyring, and Michael Polanyi50 of Arrhenius's activation energy in terms of an electronic eigenenergy surface, along with the idea of rolling a ball on this surface, introduced a completely new way of visualizing and interpreting a chemical reaction. The rival valence-bond and molecular-orbital theories proved essentially complementary, as first emphasized, in conciliatory terms, by John Van Vleck.51 Charles Coulson would put it succinctly 20 years later:52 “[There is] a kind of uncertainty relation about our knowledge of molecular structure: the more closely we try to describe the molecule, the less clear-cut becomes our description of its constituent bonds.”10 Eugene Wigner was apparently the first to calculate the electronic energy beyond the Hartree–Fock approximation (this was for metallic sodium) and he coined the term “correlation energy” for the correction that he had found.53 The next step in developing a quantum-mechanics-based theory of chemical reactions was taken by Polanyi and Eyring, who worked separately at that time. They combined their semiempirical potential-energy surfaces with considerations from quantum-statistical mechanics into the “transition-state” (Polanyi)54 and “activated-complex” (Eyring)55 theory. In the same year, John Van Vleck laid the foundations of ligand-field theory,56 by showing that in coordination compounds “electrons from a paramagnetic cation are allowed to wander onto the anions and vice versa, so that there is incipient covalence.”57 The timeline of Figure 2 also includes the discovery of nuclear fission, as it tops the development of the notion of the chemical element, discussed above. On the institutional side, the rise of physical and theoretical chemistry was fostered by the following developments: The Faraday Society58 was founded in London, named after a founder of electrochemistry. The German Society for Electrochemistry (since 1902 the Bunsen Society), dedicated to physical chemistry and electrochemistry,59 was founded, with Ostwald serving as its first president. In Germany, the Kaiser Wilhelm Society for the Advancement of Science (today the Max Planck Society) was founded. One of its first two institutes was dedicated to physical chemistry, with Fritz Haber as its founding director.60 The first chair in theoretical chemistry was established at the University of Cambridge, for John Lennard-Jones who would speak of his operation as a “mathematical laboratory.”61 Additional journals for physical chemistry were established, Journal de Chimie Physique in France and Faraday Transactions in Britain, among others. The most important development in terms of publication venues for the post-quantum-revolution physical chemistry was perhaps the founding of the Journal of Chemical Physics (JCP), with Harold Urey as Editor-in-Chief. JCP provided a venue for publishing purely theoretical papers, which the competing Journal of Physical Chemistry (JPC) had scoffed at. In any case, Harold Urey would characterize publishing in the then-failing JPC as “burial without a tombstone.”62 In the very first issue of JCP one can find such gems as John Slater's analysis of the covalent bond in terms of the quantum virial theorem, apart from contributions by Langmuir, Debye, Pauling, G. N. Lewis, Eyring, and others. JCP became a triumph of physical chemists oriented towards physics and mathematics. Ostwald's 19th century premise that the road to general chemistry goes through physics and mathematics thus found a new gratification.22 This concludes the tour of the first heroic eras of physical and theoretical chemistry, characterized by the co-optations of thermodynamics and quantum mechanics. Figure 2 also contains an admonition that affects the current era, which is characterized by the co-optation of computational techniques and a reliance on the digital computer. It comes from none other than Richard Feynman. Feynman was a one-time theoretical chemist himself—he discovered what's known as the Hellmann–Feynman theorem as an undergraduate working with John Slater. Here's his advice:63 “[I]f you want to make a simulation of nature, you'd better make it quantum mechanical …” Well, possibly—or hopefully—the quantum simulator or quantum computer will render the arsenal of approximations developed to treat chemical problems redundant as computational tools and make theoretical chemistry truly predictive.64 Of course only if there will ever be a universal quantum computer … Henceforth, I will take a somewhat myopic view and describe the key developments concerning physical and theoretical chemistry in Berlin and Leipzig. In doing so, I will present a gallery of the main contributors to these developments working out of these two centers. A gallery of the Leipzig professors of physical chemistry is shown in Figure 3. The first physical chemistry chairs at Leipzig. From left to right: Wilhelm Ostwald (1853–1932), Max Le Blanc (1865–1943), and Karl Friedrich Bonhoeffer (1899–1957). The beginnings of Wilhelm Ostwald at Leipzig, upon his arrival from Riga, were less than glamorous: the building was “an old pile in every way unfitted for the carrying on of those delicate experiments which brought Ostwald to the forefront of scientific workers.”65 Moreover, Ostwald had to teach freshman analytical and pharmaceutical chemistry, a job beneath the dignity of Johannes Wislicenus, the dominant chemist at Leipzig at the time.11 Then finally, in 1898, the university and the government of Saxony provided Ostwald with the present, much more adequate building, designed by Ostwald himself.66 As a commentator writing for the journal Nature put it at the time, the building was “a proof of the appreciation of the importance of the new science and of Ostwald's services.”65 The well-attended inauguration of Ostwald's institute (Figure 4) served to celebrate the new field of physical chemistry. Inauguration of Ostwald's institute in Leipzig, with Ostwald at the lectern and S. Arrhenius, J. van't Hoff, W. Nernst, M. Planck, G. H. Wiedemann, H. Landolt, J. Wislicenus, and others in the audience. Following his early retirement, in 1906, Ostwald continued to flourish in a great number of areas, ranging from philosophy to painting to peace activism. His credo, “Don't squander energy, utilize it” is modern in both its literal and figurative sense. Max Le Blanc was something of a Fritz Haber doppelgänger, in that he studied in Berlin under August Wilhelm von Hofmann and held a professorship at the Technische Hochschule Karlruhe. However, in the intervening years he was, unlike Haber, admitted by Ostwald as his assistant and Habilitand. After Ostwald's retirement in 1906, Le Blanc became Ostwald's successor at Leipzig. Thereby he vacated the professorial slot at Karlsruhe, which had been filled by appointing Haber as Ordinarius.12 Karl Friedrich Bonhoeffer was a pupil of Walther Nernst, assistant of Fritz Haber and Le Blanc's successor at Leipzig. The Bonhoeffer family—particularly Karl Friedrich's brother Dietrich and sister Christine—put up a heroic resistance to the Hitler regime.67 After World War II, Karl Friedrich Bonhoeffer was intensely involved in the reconstruction of German Academia, which he served in various capacities—mostly simultaneously. His wide-ranging scientific pursuits included the kinetic studies of chemical and biochemical reactions, in which he pioneered the use of deuteration as a means to unravel reaction mechanisms.13 A gallery of the Berlin professors of physical chemistry is shown in Figure 5. The first physical chemistry professors in Berlin. Clockwise from top left: Hans Landolt (1831–1910), Jacobus van't Hoff (1852–1911), Walther Nernst (1864–1941; portrait by Max Liebermann, 1911, Max Volmer (1885–1965), Max Bodenstein (1871–1941), and Fritz Haber (1868–1934). Hans Landolt was the first occupant of the newly created chair for physical chemistry at the Berlin University. A pupil of Robert Bunsen, Landolt dedicated his life to the study of the relationship between chemical composition and the physical properties of substances.6814 His name is connected with the standard reference work, the Landolt–Börnstein tables, whose first edition appeared in 1883. Today, the tables comprise about 400 volumes and are available as a database.69 It was at the occasion of Landolt's induction into the Prussian Academy that Emil du Bois-Reymond, its perpetual secretary, used the phrase that “physical chemistry is the chemistry of the future.”24 Jacobus van't Hoff came to Berlin in 1896 when his accomplishments were legion.70 Here I will mention just a few more, in addition to his pioneering work in chemical thermodynamics outlined above.15 In his 1874 dissertation, van't Hoff laid the foundations of stereochemistry, by introducing the prescient hypothesis that the bonds of carbon atoms are directed towards the vertices of a tetrahedron.71 Pauling would justify it 57 years later by his theory of directed valence.72 Van't Hoff's work on osmotic pressure established an analogy between gaseous mixtures and solutions and became a basis for the accurate determination of molecular weights. Van't Hoff also cared about the implications of his work for plant as well as animal biology.73 Van't Hoff played a truly unique role in chemistry: When he was a student, organic structural chemistry dominated much of the field. There were zillions of useful rules to guide the synthesis of new compounds—but no chemical theory. By unleashing thermodynamics on chemical problems, van't Hoff established a lasting theoretical basis for chemistry. Chemical thermodynamics became the theoretical chemistry of van't Hoff's day and a component any theoretical chemistry of the future. From this perspective, it is perhaps less surprising that van't Hoff was chosen to be the recipient of the very first Nobel Prize in Chemistry. The great organic chemist Emil Fischer received only the second. The two other members of the Ionist triumvirate would be honored likewise, all during the first decade of the award. Along with the Chemistry Nobel Prizes for William Ramsay and Ernest Rutherford, one-half of the chemistry prizes during the first decade went to physical chemists or physicists. According to my count, over the long term about one-third of the Chemistry Nobels have gone to physical/theoretical chemists or physicists. Landolt's successor at Berlin University was Ostwald's former assistant Walther Nernst. After a stint at Göttingen, Nernst arrived, in his automobile, in Berlin in 1905 (Figure 6), to take up the vacated chair. The next year, Wilhelm Ostwald retired from his post in Leipzig, thereby clearing the way for Berlin's dominance of the field of physical chemistry. Moreover, Nernst heralded his arrival in Berlin with a roar—by enunciating his Heat Theorem (or Third Law of Thermodynamics). The experimental and theoretical basis for the Third Law remained at the focus of his research in subsequent years, which also cemented Berlin's position as one of the early centers of the young quantu
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