Arrhenius, Svante August

(b. Vik, Sweden, 19 February 1859; d. Stockholm, Sweden, 2 October 1927)

chemistry, physics.

Svante August Arrhenius, one of the founders of modern physical chemistry, came from a Swedish farming family. His father, Svante Gustav Arrhenius, was a surveyor and later a supervisor of the University of Uppsala. He also was employed as overseer on the ancient estate of Vik (Wijk), on Lake Målar near Uppsala. In 1855 he married Carolina Christina Thunberg: Svante August was their second son. By the beginning of 1860, the father’s position had improved enough so that the family moved to Uppsala, where he could devote full time to his university position.

After attending the Cathedral School in Uppsala, Arrhenius entered the University of Uppsala at the age of seventeen. He studied mathematics, chemistry, and physics, and passed the candidate’s examination in 1878. Arrhenius chose physics as the principal subject for his doctoral study, but he was not satisfied with his chief instructor, Tobias Robert Thalén, Although Thalén was an eminent and competent experimental physicist and lecturer, he was interested only in spectral analysis. Arrhenius went to Stockholm in 1881 with the intention of working under Erik Edlund, physicist of the Swedish Academy of Sciences. The results of his first independent research, entitled “The Disappearance of Galvanic Polarization in a Polarization Vessel, the Plates of Which Are Connected by Means of a Metallic Conductor,” was published in 1883. During the winter of 1882–1883 Arrhenius determined the conductivity of electrolytes; this resulted in his doctoral dissertation (1884), in which he discussed the electrolytic theory of dissociation. He presented it to the University of Uppsala and defended it in May 1884, but his dissertation was awarded only a fourth class (non sine laude approbatur, “approved not without praise”) and his defense a third (cum laude approbatur, “approved with praise”). According to the then prevailing custom, this was not sufficient to qualify him for a docentship, which was a bitter disappointment to Arrhenius.

The chemist Sven Otto Pettersson, professor of chemistry at the Technical High School of Stockholm, reviewed Arrhenius’ dissertation in the journal Nordisk Revy and praised it very highly, however: “The faculty have awarded the mark non sine laude to this thesis. This is a very cautious but very unfortunate choice. It is possible to make serious mistakes from pure cautiousness. There are chapters in Arrhenius’ thesis which alone are worth more or less all the faculty can offer in the way of marks.”¹ Pettersson referred here to the discovery of the connection between conductivity and speed of reaction. Per Theodor Cleve, speaking to Ostwald during the latter’s visit to Uppsala, remarked, “But it is nonsense to accept with Arrhenius that in a solution of potassium-chloride chlorine and potassium are separated from each other,” and in his speech honoring Arrhenius at the Nobel banquet in 1903 he said: “These new theories also suffered from the misfortune that nobody really knew where to place them. Chemists would not recognize them as chemistry; nor physicists as physics. They have in fact built a bridge between the two.”

Arrhenius sent copies of his thesis to a number of prominent scientists: Rudolf Clausius in Bonn, Lothar Meyer in Tübingen, Wilhelm Ostwald in Riga, and Jacobus Henricus van’t Hoff in Amsterdam. Ostwald, a physical chemist and professor at the Polytechnikum in Riga, was deeply impressed by the paper. He visited Arrhenius in Uppsala in August 1884, and offered him a docentship in Riga. Thanks to this, Arrhenius was appointed lecturer in physical chemistry at the University of Uppsala in November of that year. The English physicist Oliver Lodge was also impressed by Arrhenius’ paper, and wrote an abstract and critical analysis of it for the Reports of the British Association for the Advancement of Science in 1886.

Through the influence of Edlund, Arrhenius received a travel grant from the Swedish Academy of Sciences which made it possible for him to work in the laboratories of Ostwald in Riga (later in Leipzig), Kohlrausch in Würzburg, Ludwig Boltzmann in Graz, and van’t Hoff in Amsterdam. During these Wanderjahre (1886–1890), he further developed the theory of electrolytic dissociation. Arrhenius’ theory was, however, slowly accepted at first, but because of neglect rather than active opposition. It was the enthusiasm and influence of Ostwald and van’t Hoff that helped to make it widely known. In 1887 Arrhenius met Walther Nernst in Kohlrausch’s laboratory. There, too, he carried out an important investigation on the action of light on the electrolytic conductivity of the silver salts of the halogens. In 1891 Arrhenius received an invitation from the University of Giessen, but he preferred the post of lecturer at the Technical High School in Stockholm, where he was appointed professor of physics in 1895 and was rector from 1896 to 1905. After refusing an offer from the University of Berlin, he became director of the physical chemistry department of the newly founded Nobel Institute in Stockholm, a post which he held until his death.

One of Arrhenius’ first honors was election as honorary member of the Deutsche Elektrochemische Gesellschaft in 1895. In 1901 he was appointed to the Swedish Academy of Sciences, over strong opposition. The following year he received the Davy Medal from the Royal Society of London, and in 1903 he won the Nobel Prize for chemistry “in recognition of the extraordinary services he has rendered to the advancement of chemistry by his theory of electrolytic dissociation.” Arrhenius was elected an honorary member of the Deutsche Chemische Gesellschaft in 1905; he became a foreign member of the Royal Society of London six years later. During his visit to the United States in 1911, Arrhenius was awarded the first Willard Gibbs Medal. In 1914 he received the Faraday Medal.

Arrhenius was married twice: in 1894 to his best pupil and assistant, Sofia Rudbeck, and in 1905 to Maria Johansson. By the first marriage he had one son, Olof, and by the second, a son, Sven, and two daughters, Ester and Anna-Lisa.

Arrhenius’ aim, during his study of the conductivity of electrolytic solutions at Edlund’s laboratory, was to find a method for determining the molecular weight of dissolved nonvolatile compounds by measuring electric conductivity. Soon he recognized that the state of the electrolyte was the matter of primary importance. Arrhenius completed his experimental work in the spring of 1883 and submitted a long memoir (in French) to the Swedish Academy of Sciences on 6 June 1883, with the results of his experiments and the conclusions he deduced from them. The memoir was published in 1884 under the title “Recherches sur la conductibilité galvanique des électrolytes.” The first part (“La conductibilité des solutions aqueuses extrément diluées” and “Recherches sur la conductibilité galvanique des électrolytes”) contains his findings on the conductivity of many extremely dilute solutions. Instead of measuring the conductivities with the exact alternating-current method, which Kohlrausch had introduced in 1876, Arrhenius used a “depolarizer,” devised by Edlund in 1875, which corresponded roughly to a hand-driven rotating commutator.

In the first part of his memoir, Arrhenius gave an account of his experimental work: He measured the resistance of many salts, acids, and bases at various dilutions to 0.0005 normal (and sometimes to even lower concentrations), and gave his results so as to show in what ratio the resistance of an electrolyte solution is increased when the dilution is doubled. It is true that Heinrich Lenz and Kohlrausch had made similar measurements, but they did not use such great dilutions. Like Kohlrausch, Arrhenius found that for very dilute solutions the specific conductivity of a salt solution is in many cases nearly proportional to the concentration (thesis 1) when the conditions are identical. The conductivity of a dilute solution of two or more salts is always equal to the sum of the conductivities that solutions of each of the salts would have at the same concentration (thesis 2). Furthermore, the conductivity of a solution equals the sum of the conductivities of salt and solvent (thesis 3).

If these three laws are not observed, it must be because of chemical action between the substances in the solution (theses 4 and 5). The electrical resistance of an electrolytic solution rises with increasing viscosity (thesis 7), complexity of the ions (thesis 8), and the molecular weight of the solvent (thesis 9). Thesis 9 is an example of a proposition that is not correct. In addition to the viscosity of the solvent, its dielectric constant, not the molecular weight, is significant. Arrhenius worked, however, with a limited number of solvents (water, several alcohols, ether) for which the dielectric constant decreases approximately as the molecular weight rises. Arrhenius summarized Part I of his memoir as follows:

In the first six sections of the present work we have described a new method of measuring the resistance of electrolytic solutions. In this method we made use of rapidly alternating currents, produced by a depolarizer constructed for the purpose by M. Edlund. We have tried to show the use of this method, and to make clear the practical advantages which it possesses.

The main importance of Arrhenius’ memoir, however, does not lie in the experimental measurements or in the thirteen detailed deductions of Part I, but in his development of general ideas. These contain the germ of the theory of electrolytic dissociation (which received its definitive statement only three years later).

In Part II (“Théorie chimique des électrolytes”), Arrhenius gave a theoretical treatment of his experimental work, which he based on the hypothesis of the British chemist Alexander William Williamson and the German physicist Rudolf Clausius. In his famous article “Theory of Aetherification,” Williamson suggested that in a chemical system a molecule continually exchanges radicals or atoms with other molecules, so that there is a state of dynamic equilibrium between atoms and molecules. Thus, in hydrochloric acid “each atom of hydrogen does not remain quietly in juxtaposition with the atom of chlorine with which it first united, but, on the contrary, is constantly changing places with other atoms of hydrogen, or, what is the same thing, changing chlorine.” Williamson, however, did not assume that the radicals or atoms were electrically charged. Clausius advanced the hypothesis that a small fraction of a dissolved salt is dissociated into ions even when no current is passing through the solution. He did not state or calculate how much of the salt is thus affected.

Arrhenius stated that the dissolved molecules of an electrolyte are partly “active,” partly “inactive”: “The aqueous solution of any hydrate [by hydrates Arrhenius always meant hydrogen compounds like acids and bases] is composed, in addition to the water, of two parts, one active, electrolytic, the other inactive, non-electrolytic. These three substances, viz. water, active hydrate, and inactive hydrate, are in chemical equilibrium, so that on dilution the active part increases and the inactive part diminishes” (thesis 15). Arrhenius gave no precise account of the nature of the active and inactive parts, however; he only indicated what they might be. He extended his hypothesis to other dissolved electrolytes (salts) and defined the “coefficient of activity of an electrolyte” (corresponding to our notion of degree of electrolytic ionization) as “the number expressing the ratio of the number of ions actually contained in the electrolyte to the number of ions it would contain if the electrolyte were completely transformed into simple electrolytic molecules.” In 1890 Arrhenius said that he chose the name “activity coefficient” instead of “degree of electrolytic dissociation” on grounds of prudence!²

After thesis 16 we find a number of chemical applications. Arrhenius asserted that “the strength of an acid is the higher, the greater its activity coefficient. The same holds for bases.” The dissociation becomes complete at infinite dilution of the solution (thesis 31); and in solutions of salts of weak acids, strong acids displace the weak acids (thesis 34). From a chemical point of view, thesis 23 is important: “When the relative amounts of ions A, B, C, and D are given, the final result is independent of their original form of combination, whether AB and CD, or AD and BC.” The principle of the calculation of the degree of hydrolyzation by means of the law of mass action is given in thesis 29: “Every salt, dissolved in water, is partly dissociated in acid and base. The amount of the decomposition products is greater the weaker the acid and the base and the greater the amount of water.”

In the last thesis (56), Arrhenius clearly stated the constancy of the heat of neutralization of a strong acid with a strong base: “The heat of neutralisation, set free by the transformation of a perfectly active base, and perfectly active acid, into water and simple salt, is only the heat of activity of the water,” where “heat of activity” is the heat used in transforming a body from the inactive to the active state. Arrhenius ended his memoir with a long summary, which begins as follows:

In the present part of this work we have first shown the probability that electrolytes can assume two different forms, one active, the other inactive, such that the active part is always, under the same exterior circumstances (temperature and dilution), a certain fraction of the total quantity of the electrolyte. The active part conducts electricity, and is in reality the electrolyte, not so the inactive part. ³

Although Arrhenius discussed electrolytic dissociation in his memoir of 1884, he nowhere used the word “dissociation,” nor is there any explicit identification of the “active part” of the electrolyte with free ions in the solution. It is not so surprising that the acceptance of his theory was slow at first, above all because it had to overcome preconceived ideas that oppositely charged ions could not exist separately in solution. The influence and enthusiasm of Ostwald and van’t Hoff were consequently needed to make it widely known and accepted.

The next step toward a definite and clear electrolytic dissociation theory came from a famous memoir of van’t Hoff, “The Role of Osmotic Pressure in the Analogy Between Solutions and Gases” (1887). Van’t Hoff recognized in this memoir an analogy between dilute solutions and gases: “The pressure which a gas exerts at a given temperature, if a definite number of molecules is contained in a definite volume, is equal to the osmotic pressure which is produced by most substances under the same conditions, if they are dissolved in any given liquid.” He showed that it was possible to write for solutions an equation PV = iRT, analogous to the gas equation where P is the osmotic pressure instead of the gaseous pressure, R the gas constant, V the volume, T the absolute temperature, and i a coefficient that is sometimes equal to unity but for the salts is greater than unity. Thus, van’t Hoff concluded that the law was valid only for the “great majority of substances,” but he could not explain the fact that solutions of salts acids, and bases possess greater osmotic pressure, higher vapor tension, and greater depression of the freezing point than the results calculated from Raoult’s experiments. Van’t Hoff made no attempt to explain this exception, but Arrhenius identified the number of ions in solution with the value of i. In a letter to van’t Hoff, dated 30 March 1887, Arrhenius wrote: “Your paper has cleared up for me to a remarkable degree the constitution of solutions... Since... electrolytes decompose into their ions, the coefficient i must lie between unity and the number of ions.” He continued with a statement of the theory of electrolytic dissociation in a clear and definite form: “In all probability all electrolytes are completely dissociated at the most extreme dilution.”

In 1887 Arrhenius published a much revised, extended, and consolidated version of his theory of electrolytic dissociation in its quantitative formulation under the title “Ueber die Dissociation der im Wasser gelösten Stoffe.” He wrote:

In a previous communication.... I have designated those molecules whose ions have independent motion, active molecules, and those whose ions are bound together, inactive molecules. I have also maintained it probable that at the most extreme dilution all the inactive molecules of an electrolyte are converted into active molecules, On this assumption I will base the calculations now to be carried out. The ratio of the number of active molecules to the total number of molecules, active and in active, I have called the activity coefficient. The activity coefficient of an electrolyte at infinite dilution is therefore taken as unity. At smaller dilutions it is less than unity... ⁴

Arrhenius calculated the degree of electrolytic dissociation quantitatively as the ratio of the actual molecular conductivity of the solution and the limiting value to which the molecular conductivity of the same solution approaches with increasing dilution. He then gave the relationship between van’t Hoff’s constant i and the degree of ionization or activity coefficient α in the form i =1 + (k – 1)α, where k is the number of ions into which the molecule of the electrolyte dissociates. He compared the values of i calculated from Raoult’s freezing-point data of solutions in water with the values obtained from the molecular conductivity for twelve nonconductors, fifteen bases, twenty-three acids, and forty salts, and found a very satisfactory agreement. He concluded that van’t Hoff’s law holds good, not merely for the majority but for all substances, including electrolytes in aqueous solution. “Every electrolyte in aqueous solution consists in part of molecules electrolytically and chemically active and in part of inactive molecules, which, however, on dilution change into active molecules, so that at infinite solution only active molecules are present.”⁵ With this publication, the full statement of the theory of electrolytic dissociation was given, and soon received substantial confirmation.

Among Arrhenius’ most important contributions to this theory are his publications on isohydric solutions, solutions of two acids that can be mixed without any change in the degree of dissociation (1888); the relation between osmotic pressure and lowering of vapor tension (1889); the heat of dissociation of electrolytes and the influence of temperature on the degree of dissociation (1889); the condition of equilibrium between electrolytes (1889); the determination of electrolytic dissociation of salts through solubility experiments (1892); the hydrolysis of salts and weak acids and weak bases (1894); and the alteration of the strength of weak bases by the addition of salts (1899).

A problem that had always held Arrhenius’ attention was the abnormality of strong electrolytes that do not follow Ostwald’s law of dilution, which can be obtained by applying the law of mass action to the equilibrium between the dissociated and undissociated parts of an electrolyte. Arrhenius stated clearly that the law of mass action is not applicable to strong electrolytes, even when they are very diluted. A theory for the modern treatment of strong electrolytes was given by the Danish chemist Niels Bjerrum, by the Dutch-American scholar Peter Joseph Debye, and by the German Erich Hückel, who based their treatment on electrical interactions between the ions in solution.

Among the other physical-chemical works of Arrhenius, his important theoretical contribution, “Ueber die Reaktionsgeschwindigkeit bei der Inversion von Rohrzucker durch Säuren” (1889) must be mentioned. In this publication, Arrhenius studied the influence of an increase in temperature on the reaction velocity. Using the equilibrium equation deduced by van’t Hoff in 1884, which gives mathematically the relation between the velocity coefficient and the temperature, Arrhenius realized that the study of the temperature coefficients of reaction velocity is important from the point of view of the general mechanism of chemical change. From the observation that the reaction velocity shows an abnormal increase of 10 to 15 per cent for one degree in temperature, Arrhenius supposed that active cane sugar molecules are formed; these activated molecules (with much greater than average energy) are more susceptible to reaction. In a reaction system there are only a certain number of “active” molecules that can undergo reaction. This idea that molecules require a certain critical energy in order to react, as well as the concept of activation energy, is of great significance in modern chemistry.

During the last twenty-five years of his life, Arrhenius’ interests were diverted to other fields of science, especially to the physics and chemistry of cosmic and meteorological phenomena. His contribution to these subjects consists mostly in the application of the laws of theoretical chemistry to existing astronomical, geophysical, and geological observations. Besides a short treatise on ball lightning (1883) and a publication on the influence of the rays of the sun on the electric phenomena of the earth’s atmosphere (1888), Arrhenius and the meteorologist Nils Ekholm investigated the influence of the moon on the electric state of the atmosphere, on the aurora, and on thunderstorms (1887). Arrhenius supposed in the 1888 article that electric charges originate from ionization of the air by ultraviolet rays.

In 1896 he published a long memoir “On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground,” in which he developed a theory for the explanation of the glacial periods and other great climatic changes, based on the ability of carbon dioxide to absorb the infrared radiation emitted from the earth’s surface. Although the theory was based on thorough calculations, it won no recognition from geologists. In 1898 Arrhenius wrote a remarkable paper on the action of cosmic influence on physiological processes.

“Zur Physik des Vulkanismus,” published in 1901, was also based on physical-chemical facts. Although at normal temperature, water is an acid about a hundred times weaker than silicic acid, increasing ionic dissociation with increased temperature would at a few hundred degrees make water a stronger acid than silicic acid. Arrhenius calculated by extrapolation that water at 1000°C. is eighty times, and at 2000°C. 300 times, stronger than silicic acid. In the magma, water penetrates at a temperature of between 1000°C. and 2000°C., and decomposes silicates. The magma expands, its volume increases, and it penetrates into the fissures of volcanoes. When the rising magma is cooled, the reverse process takes place, water is liberated, and under low pressure violent explosions occur, leading to volcanic eruptions. However, the hypothetical reaction between the molten silicate and water was not tenable, and Arrhenius’ theory was soon forgotten.

In 1903 Arrhenius published his Lehrbuch der kosmischen Physik, the first textbook on cosmic physics. His work on the cosmic effects of the pressure of light rays attracted deserved attention in professional circles. With the aid of very light mirrors in a vacuum, the Russian physicist Pëtr Nikolajevich Lebedev and the American physicists Ernest Fox Nichols and Gordon Ferrie Hull proved in 1901 that a ray of light that meets material particles exerts a pressure on them, as James Clerk Maxwell had predicted in his electromagnetic theory of light. Arrhenius applied the radiation pressure to various phenomena even before its experimental confirmation. He calculated that we might expect streams of minute particles to be shot out from the sun in all directions. Arrhenius explained phenomena of the solar corona, comets, the aurora, and the zodiacal light by these charged particles, many of which, he said, would be electrically charged by ionization in the gaseous atmosphere of the sun. In 1905 he applied this concept to the problem of the origin of life by assuming that living seeds, spores, and so forth could be transported from interstellar space by the pressure of light (panspermic theory). Since Arrhenius’ basic idea of the universe was its infinity in time, he did not have any need for a hypothesis involving a singular event like the creation of life. His concept that there was no beginning and no end of the universe follows from his inability to resolve by any other means the paradox in the application of the first and second laws of thermodynamics to the universe. According to Clausius, the energy of the world is constant and the entropy approaches a maximum, so that the universe is tending to what he called the Wärmetod (“heat death”) through exhaustion of all sources of heat and motion. Now, if the universe were assumed to have a finite lifetime, the creation of energy at some time would be required—and this is contrary to the first law of thermodynamics. On the other hand, if the universe were assumed to have existed for an infinite time, according to the second law of thermodynamics, the maximum entropy would have been achieved. To solve the paradox, Arrhenius assumed that it is possible that there are galaxies in the universe where processes take place with decreasing entropy. His last paper (1927) was on thermophilic bacteria and the radiation pressure of the sun. In it he stated that on earth there are thermophilic bacteria that exist in volcanic areas at temperatures between 40°C. and 80°C. The temperature of the surface of the planet Venus is 50°C., and Arrhenius thought that it was possible that these bacteria are transported from Venus to earth by radiation pressure. Of course, he did not know of the existence of cosmic radiation, which makes it physically impossible for unprotected living things to survive transportation through interplanetary space.

In addition to his cosmic researches, Arrhenius was concerned with the theory of immunity, an interest that resulted in two textbooks: Immunochemistry (1907) and Quantitative Laws in Biological Chemistry (1915). After working during the summer of 1902 in the Frankfurt laboratory of the German bacteriologist Paul Ehrlich, Arrhenius and the Danish bacteriologist Thorvald Madsen (later founder and director of the Danish State Serum Institute at Copenhagen) published a paper on physical chemistry applied to toxins and antitoxins (1902). Against Ehrlich, who in his “side-chain theory” regarded the mutual relationship of toxins and antitoxins as a phenomenon of chemical neutralization, Arrhenius postulated a chemical equilibrium between toxin and antitoxin which follows the ordinary mass action law. The immunological phenomenon of antitoxin action was linked to the interaction of a weak acid and a weak base.

Besides the textbooks on immunochemistry and cosmic physics mentioned above, Arrhenius wrote a number of scientific books: Lärobok i teoretisk elektrokemi (1900), Theorien der Chemie (1906), and Theories of Solution (the Silliman Lectures of 1911, published in 1912). Arrhenius devoted most of his later years to popularizing science. His books and articles had a simple but always scientific approach, and were immediate worldwide successes. They were translated into several languages and appeared in numerous editions. Among these are Världnarnas utveckling (1906), Människan inför världsgåtan (1907), Das Schicksal der Planeten (1911), and Stjärnornas Öden (1915). His Kemien och det moderna livet (1919) contains a popular scientific treatment of the significance and the problems of technical chemistry. These books give a good idea of Arrhenius’ aptitude for scientific speculation, a penchant also exhibited in his original ideas in cosmic physics, meteorology, immunology, and in his greatest contribution to chemistry, the theory of electrolytic dissociation.

NOTES

1.Nordisk revy (15 December 1884); cf. Svensk kemisk tidskrift (1903), 208.

2.Svensk kemisk tidskrift (1890), 9.

3.Bihang till K. Svenska Vet.-Akad. Handlingar, 8 , no. 14 (1884), 87.

4.Zeitschrift für phys. Chemie, 1 (1887), 632.

5.Ibid., p. 637.

BIBLIOGRAPHY

For a bibliography of Arrhenius’ works and writings, see E. H. Riesenfeld, Svante Arrhenius (Leipzig, 1931), pp. 93–110. In the bibliography given below, the following abbreviations are used: Bihang (Bihang till kungliga vetenskapsakademiens handlingar); Öfversigt (Öfversigt af kungliga vetenskapsakademiens för handlingar); Meddelanden (Meddelanden frän kungliga vetenskatsakademiens Nobelinstitut); Z. phys. Chem. (Zeitschrift für physikatlische Chemie).

I. Original Works. Articles that are autobiographical or deal with the history of the theory of electrolytic dissociation are “The Development of the Theory of Electrolytic Dissociation,” in Les prix Nobel en 1903 (Stockholm, 1905); Proceedings of the Royal Institute, 17, pt. 3 (1906); and Nobel Lectures Chemistry 1901–1921 (Amsterdam-New York-London, 1966), pp. 45–58; “Electrolytic Dissociation,” in Journal of the American Chemical Society, 34 (1912), 353–364; “Aus der Sturm-und Drangzeit der Lösungstheorien,” in Chemisch weekblad, 10 (1913), 584–599; “The Theory of Electrolytic Dissociation,” in Lectures Delivered Before the Chemical Society (London, 1928), pp. 237–249.

Articles by Arrhenius concerning the theory of electrolytic dissociation are “Recherches sur la conductibilité galvanique des électroytes,” in Bihang, 8 , no. 13 (1884) and no.14(1884). translated as Untersuchungen über die galvanische Leitfähigkeit der Elektrolyte, in Ostwald’s Klassiker der exakten Wissenschaften, no. 160 (Lepsing, 1907); “Ueber die Dissociation der im Wasser gelösten Stoffe,” in Z. phys. Chem., 1 (1887), 631–648, expanded from two papers published in Öfversigt (1887), pp. 405–414, 561–575, and translated in the Alembic Club Reprints, no. 19 (Edinburgh, 1929); “Theorie der isohydrischen Lösungen,” in Öfversigt (1888), pp. 233–247, and Z. phys. Chem2 (1888), 284–295; “Einfache Ableitung der Beziehung zwischen osmotischem Druck und Erniedrigung der Dampfspannung,” in Z. phys. Chem., 3 (1889), 115–119; “Ueber die Dissociationswärme und den Einfluss der Temperatur auf den Dissociationsgrad der Elektrolyte,” ibid., 4 (1889), 96–116; “Ueber die Gleichgewichtsverhältnisse zwischen Elektrolyten,” in Öfversigt (1889), pp. 619–645, and Z. phys. Chem., 5 (1890), 1–22; “Ueber die Bestimmung der elektrolytischen Dissociation von Salzen mittelst Löslichkeitsversuchen,” in Öfversigt (1892), pp. 481–494, and Z. phys. Chem., 11 (1893), 391–402; “Ueber die Hydrolyse von Salzen schwacher Säuren und schwacher Basen,” in Z. phys. Chem., 13 (1894), 407–411; “Ueber die Aenderung der Stärke schwacher Säuren durch Salzzusatz,” ibid., 31 (1899), 197–229; “Zur Berechungsweise des Dissociationsgrades starker Elektrolyte,” ibid., 36 (1901), 28–40.

Articles on other physical-chemical subjects are “Ueber die Einwirkung des Lichtes auf das elektrische Leitungsvermögen der Haloïdsalze des Silbers,” in Zeitschrift der Wiener Akademie der Wissenschaft, 96 (1887), 831–837; “Ueber die Reaktionsgeschwindigkeit bei der Inversion von Rohrzucker durch Säuren.” in Z. phys. Chem., 4 (1889), 226–248; and “Zur Theorie der chemischen Reaktionsgeschwindigkeit,” in Bihang, 24 , no.2 (1898), and Z. phys. Chem., 28 (1899), 317–335.

Articles about meteorology and cosmic physics are “Ueber den Einfluss der Sonnenstrahlen auf die elektrischen Erscheinungen in der Erdatmosphäre,” in Meteorologische Zeitschrift, 5 (1888), 297–304, 348–360; “Ueber den Einfluss des atmosphärischen Kohlensäuregehalts auf die Temperatur der Erdoberfläche,” in Bihang, 22 no. 1 (1896), 102 ff., excerpted in Philosophical Magazine, 41 (1896), 237–276; “Die Einwirkung kosmischer Einflüsse auf die physiologischen Verhältnisse,” in Skandinavisches Archiv für Physiologie, 8 (1898), 367–426; “Zur Physik des Vulkanismus,” in Geologiska föreningens i Stockholm förhandllingar,22 no. 5 (1901), 26 ff.; “Ueber die Wärmeabsorption durch Kohlensäure,” in Öfversigt (1901), pp. 25–58, and Drudes Annalen, 4 (1901), 689–705; “Lifvets utbredning genon världsrymden,” in Nordisk tidskrift (1905), pp. 189–200, and The Monist (1905), pp. 161 ff.; “Die vermutliche Ursache der Klimaschwankungen,” in Meddelanden, 1 , no. 2 (1906); “Physikalisch-chemische Gesetzmässigkeiten bei den kosmisch-chemischen Vorgängen,” in Zeitschrift für Elektrochemie, 28 (1922), 405–411; and “Die thermophilen Bakterien und der Strahlungsdruck der Sonne,” in Z. phys. chem., 130 (1927), 516–519.

An article on serum therapy is “Anwendung der physikalischen Chemie auf das Studium der Toxine und Antitoxine,” in Festskrift v. inv. af Stat. Serum-Inst. (Copenhagen, 1902), and Z. phys. Chem., 44 (1903), 7–62, written with Thorvald Madsen.

Books by Arrhenius are Lärobok i teoretisk elektrokemi (Stockholm, 1900), translated as Text-Book on Theoretical Electrochemistry (London-New York, 1902); Lehrbuch der kosmischen Physik, 2 vols. (Leipzig, 1903); Theorien der Chemie (Leipzig, 1906), translated as Theories of Chemistry (London-New York, 1907); Immunochemistry (New York, 1907); Theories of Solution (London-New Haven, Conn., 1912); and Quantitative Laws in Biological Chemistry (New York-London, 1915).

II. Secondary Literature. Works on Arrhenius include W. Ostwald, “Svante August Arrhenius,” in Z. phys. Chem., 69 (1909), v-xx; J. Walker, “Arrhenius Memorial Lecture,” in Journal of the Chemical Society (1928), pp. 1380–1401; W. Palmaer, “Arrhenius,” in G. Bugge, Buch der grossen Chemiker (Weinheim, 1929), II, 443–462, translated and abridged by R. E. Oesper in E. Farber, ed., Great Chemists (New York, 1961), pp. 1093–1109; E. H. Riesenfeld, “Svante Arrhenius,” in Berichte der Deutschen Chemischen Gesellschaft, 63 (1930), 1–40, and Svante Arrhenius (Leipzig, 1931); and A. Olander, O. Arrhenius, A. L. Arrhenius-Wold, and G. O. S. Arrhenius, in Svante Arrhenius till 100-arsminnet av hans födelse (Stockholm, 1959).

H. A. M. Snelders

ARRHENIUS, SVANTE AUGUST

(b.Vik, near Uppsala, Sweden, 19 February 1859; d. Stockholm, Sweden, 2 October 1927), physical chemistry. For the original article on Arrhenius see DSB, vol. 1.

There was no major biography of Arrhenius in English until the Swedish-born sociologist Elisabeth Crawford (1937–2004), née Tjerneld, published her widely acclaimed Arrhenius: From Ionic Theory to the Greenhouse Effect (1996). It remains the central authority on Arrhenius, although there has since emerged growing literature on many aspects of Arrhenius’s career, in particular his theory of the greenhouse effect. In modern research Arrhenius has emerged as a more complicated personality than H. A. M. Snelders’s original DSB entry suggests. As a young man Arrhenius worried about his career prospects, and he was personally hard pressed by his Uppsala colleagues and by their very modest assessment of his dissertation. European colleagues, in particular Wilhelm Ostwald and to some extent Jacobus Henricus van't Hoff, rescued his career. With time and success he himself created a countermyth, touted in interviews in the popular media, of his early undiscovered genius, of which the Nobel Prize (1903) served as the ultimate evidence.

Overview. Arrhenius’s life was full of difficult decisions regarding where he actually belonged. He was understood in the German and Continental centers of science, but he wanted to pursue science in Sweden, where his repertoire was wider and his influence outside science deeper. At the same time he was ambivalent about Uppsala, which is why he was happy to be called to the Stockholm Högskola (not the Royal Institute of Technology) after his successful Wanderjahre in Germany, Riga (Ostwald), and Amsterdam (van't Hoff). In 1891 he started his teaching at the Högskola, became full professor in 1895 and rector for three consecutive terms. The Högskola was a private institution, free of the complicated regulations that marked the public universities, and he cherished that freedom of thought and action. It suited his personality, which was expansive and convivial, and he thrived under these favorable circumstances.

The position also suited his deep-rooted materialism, which was both scientific (commitment to atomism) and political. He had been at Uppsala during the radical 1880s, when some of his closest friends and colleagues became members of the newly founded Verdandi association. He embraced secession of Norway from the union with Sweden, and he had many Norwegian friends. Essentially an optimist, he believed in science’s active contribution to industry and social progress; however, he held reservations with respect to Ostwald’s monistic energeticism, which he found idealist and improbable.

Arrhenius’s outlook was liberal and reformist, resulting in a degree of scepticism toward Uppsala, which he considered snobbish, introspective, and conservative. By contrast, he had a very favorable view of Stockholm, a much bigger city with many ties with industrial, commercial, and political circles, of which he would himself become part, particularly during his years as rector. He used his scientific position to promote industry and made calculations of Sweden’s future energy resources. Reinforced by the Nobel Prizes and adorned with an increasing number of scientific societies, Stockholm was

becoming a center of European science, and Arrhenius predicted that Uppsala would soon be outdistanced by the capital. He did what he could to spur that development by taking students and junior colleagues and building a European network. After his Nobel Prize his network even extended to the United States, where he did a comprehensive tour in 1904 and lectured on immunochemistry at Berkeley.

Research Style. Arrhenius’s research style was as expansive as his personality and after his protracted controversies around the ionic theory he cast his net even wider. He was easily diverted by new inspirations or apparently random contacts or proposals. Much of this newer work was in cosmic physics, a field where already in 1903 he was able to publish a thousand-page Lehrbuch der kosmischen Physik. He was inspired by his Stockholm colleagues, including Otto Pettersson, Vilhelm Bjerknes, and numerous other scientists who contributed to the development of inventories of natural resources in northern Sweden, and also by a series of research expeditions to the Arctic. He was himself a member, as a hydrographer, of an expedition to Spitsbergen in 1896. In this way Arrhenius was presented with topics on which he could bring his own

skills to bear and provide new scientific ideas. Some of these ideas, on volcanoes, physiology, serology, and a multitude of other interests, proved short-lived, and some proved marginal or even considered whimsical, such as his belief in the transportation of living spores (panspermy) from outer space to Earth.

Greenhouse Effect. The same was said for a long time about his theory of the greenhouse effect, which was revived in the second half of the twentieth century. Arrhenius’s work on this problem in 1895–1896 was not driven by any attempt to understand global climatic warming, but rather the opposite, namely to understand the mechanisms behind ice ages, a central concern of Scandinavian geophysicists. The reception of Arrhenius’s greenhouse paper was almost nil until 1938, when the British engineer Guy Stewart Callendar published a paper on human climate forcing, using the greenhouse connection as a point of departure. Callendar’s ideas were also marginalized, and not until the 1970s did there emerge a common understanding that the greenhouse theory was of great significance. The latter career of Arrhenius’s theory has been less about whether the theory is correct, and more about the size of the contribution of anthropogenic greenhouse gases on measured increases in global temperatures, which could be caused by other factors whose contributions are hard to determine.

Since the late 1980s Arrhenius has become more famous as the founding figure of an understanding of global warming than for the discovery of electrolytic dissociation, for which he was awarded the Nobel Prize in 1903. A common feature of the two theories, however, is that they have been surrounded by controversy, ionic theory during his lifetime, the greenhouse effect long after his death. Indeed, almost all important work that Arrhenius did, and some of his less important work as well, drew attention and controversy. He fell out with his erstwhile friend Walther Nernst and continued to contest Nernst’s Nobel Prize, awarded 1920 and handed over in 1921, until that was no longer possible. He quarrelled incessantly with the Frankfurt immunologist Paul Ehrlich, who was not able to follow Arrhenius’s mathematical method and was more interested in therapy than in theory. That so many came to question and even to dislike Arrhenius had something to do with his easy moves between chemistry, biology, and physiology, always using the tools of physical chemistry. But on another level it was partly his fame and standing as a central figure in the expanding power centers of Stockholm that made him a local and national celebrity even before the Nobel Prize. He was a man who seemed to thrive in battle; it released his energies, it lent eloquence to his vitriolic polemics, and it provided him stamina for his fourteen-hour workdays over months and years.

Work was also a cure when human relations were a strain. Sofia Rudbeck, his first wife, started as a graduate student at the Högskola in 1892 and became his private assistant; they married in 1894. She left him the following year, revealing unusual independence and radical tendencies perhaps tinted by her emerging contacts with the theosophist movement—incompatible with the earthy materialism of her husband. The divorce was granted in July 1896. Sofia retained custody of their son, Olof Wilhelm, the divorce agreement stipulating that the father would not see his son until he was five. Briefly sustained by Alfred Nobel, Sofia endured financial hardships and later earned her living as a photographer.

Arrhenius was as popular as he was controversial. He easily made friends and kept them through his good spirits and a flood of letters. He ate and drank with the same gusto as he devoured any new topic that came his way. He was a storyteller and a witty and good-humored speaker. He also was adept at coining phrases and metaphors, sometimes at the cost of precision but with a significant effect on his career as an author of popular science, a genre he transformed. He has sometimes been disparaged as a scientist who did not like experiments. The opposite is true: He was an ardent and competent experimentalist, but he always put his ideas first, carrying out deeper investigations to test what started as intuition but could prove to be an important hypothesis.

SUPPLEMENTARY BIBLIOGRAPHY

Bensaude-Vincent, Bernadette. “Myths about a Polymath.” Nature 384 (1996): 36–37. A review of Elisabeth Crawford’s Arrhenius: From Ionic Theory to the Greenhouse Effect.

Crawford, Elisabeth. Arrhenius: From Ionic Theory to theGreenhouse Effect. Canton, MA: Science History, 1996.

Servos, John W. “A Scientific Venturer: Arrhenius, reviewed by J. W. Servos.” Science 273 (1996): 1512–1513. A review of Elisabeth Crawford’s Arrhenius: From Ionic Theory to the Greenhouse Effect.

Sörlin, Sverker. “Rituals and Resources of Natural History: The North and the Arctic in Swedish Scientific Nationalism.” In Narrating the Arctic: A Cultural History of Nordic Scientific Practices, edited by Michael T. Bravo and Sverker Sörlin, 73–122. Canton, MA: Science History, 2002.

Weart, Spencer. The Discovery of Global Warming. Cambridge, MA: Harvard University Press, 2003.

Sverker Sörlin

Arrhenius, Svante August (1859-1927)

Swedish chemist

Svante August Arrhenius was awarded the 1903 Nobel Prize in chemistry for his research on the theory of electrolytic dissociation, a theory that had won the lowest possible passing grade for his Ph.D. two decades earlier. Arrhenius's work with chemistry was often closely tied to the science of physics , so much so that the Nobel committee was not sure in which of the two fields to make the 1903 award. In fact, Arrhenius is regarded as one of the founders of physical chemistry—the field of science in which physical laws are used to explain chemical phenomena. In the last decades of his life Arrhenius became interested in theories of the origin of life on Earth, arguing that life had arrived on our planet by means of spores blown through space from other inhabited worlds. He was also one of the first scientists to study the heat-trapping ability of carbon dioxide in the atmosphere in a phenomenon now known as the greenhouse effect .

Arrhenius was born on February 19, 1859, in Vik (also known as Wik or Wijk), in the district of Kalmar, Sweden. His mother was the former Carolina Thunberg, and his father was Svante Gustaf Arrhenius, a land surveyor and overseer at the castle of Vik on Lake Mälaren, near Uppsala. Young Svante gave evidence of his intellectual brilliance at an early age. He taught himself to read by the age of three and learned to do arithmetic by watching his father keep books for the estate of which he was in charge. Arrhenius began school at the age of eight, when he entered the fifth-grade class at the Cathedral School in Uppsala. After graduating in 1876, Arrhenius enrolled at the University of Uppsala.

At Uppsala Arrhenius concentrated on mathematics, chemistry, and physics, and he passed the candidate's examination for the bachelor's degree in 1878. He then began a graduate program in physics at Uppsala, but left after three years of study. He was said to be dissatisfied with his physics advisor, Tobias Thalén, and felt no more enthusiasm for the only advisor available in chemistry, Per Theodor Cleve. As a result he obtained permission to do his doctoral research in absentia with the physicist Eric Edlund at the Physical Institute of the Swedish Academy of Sciences in Stockholm.

The topic Arrhenius selected for his dissertation was the electrical conductivity of solutions. In 1884 Arrhenius submitted his thesis on this topic. He hypothesized that when salts are added to water they break apart into charged particles now known as ions. What was then thought of as a molecule of sodium chloride, for example, would dissociate into a charged sodium atom (a sodium ion) and a charged chlorine atom (a chloride ion). The doctoral committee that heard Arrhenius's presentation in Uppsala was unimpressed by his ideas. Among the objections raised was the question of how electrically charged particles could exist in water. In the end the committee granted Arrhenius his Ph.D., but with a score so low that he did not qualify for a university teaching position.

Convinced that he was correct, Arrhenius had his thesis printed and sent it to a number of physical chemists on the continent, including Rudolf Clausius, Jacobus van't Hoff, and Wilhelm Ostwald. These men formed the nucleus of a group of researchers working on problems that overlapped chemistry and physics, developing a new discipline that would ultimately be known as physical chemistry. From this group Arrhenius received a much more encouraging response than he had received from his doctoral committee. In fact Ostwald came to Uppsala in August 1884 to meet Arrhenius and to offer him a job at Ostwald's Polytechnikum in Riga. Arrhenius was flattered by the offer and made plans to leave for Riga, but eventually declined for two reasons. First, his father was gravely ill (he died in 1885), and second, the University of Uppsala decided at the last moment to offer him a lectureship in physical chemistry.

Arrhenius remained at Uppsala only briefly, however, as he was offered a travel grant from the Swedish Academy of Sciences in 1886. The grant allowed him to spend the next two years visiting major scientific laboratories in Europe , working with Ostwald in Riga, Friedrich Kohlrausch in Würzburg, Ludwig Boltzmann in Graz, and van't Hoff in Amsterdam. After his return to Sweden, Arrhenius rejected an offer from the University of Giessen, Germany, in 1891 in order to take a teaching job at the Technical University in Stockholm. Four years later he was promoted to professor of physics there. In 1903, during his tenure at the Technical University, Arrhenius was awarded the Nobel Prize in chemistry for his work on the dissociation of electrolytes.

Arrhenius remained at the Technical University until 1905 when, declining an offer from the University of Berlin, he became director of the physical chemistry division of the Nobel Institute of the Swedish Academy of Sciences in Stockholm. He continued his association with the Nobel Institute until his death in Stockholm on October 2, 1927.

Although he will be remembered best for his work on dissociation, Arrhenius was a man of diverse interests. In the first decade of the twentieth century, for example, he became especially interested in the application of physical and chemical laws to biological phenomena. In 1908 Arrhenius published a book entitled Worlds in the Making in which he theorized about the transmission of life forms from planet to planet in the universe by means of spores.

Arrhenius's name has also surfaced in recent years because of the work he did in the late 1890s on the greenhouse effect. He theorized that carbon dioxide in the atmosphere has the ability to trap heat radiated from the Earth's surface, causing a warming of the atmosphere. Changes over time in the concentration of carbon dioxide in the atmosphere would then, he suggested, explain major climatic variations such as the glacial periods. In its broadest outlines, the Arrhenius theory sounds similar to current speculations about climate changes resulting from global warming .

See also Atmospheric chemistry; Greenhouse gases and greenhouse effect

Svante August Arrhenius

The Swedish chemist and physicist Svante August Arrhenius (1859-1927) is known for his theory of electrolytic dissociation.

Svante Arrhenius was born on Feb. 19, 1859, at Vik near Uppsala, the son of Svante Gustav and Carolina Thunberg Arrhenius. His father was a land surveyor and later a supervisor at the University of Uppsala.

Arrhenius's intellectual abilities became obvious early. Against his parents' wishes, the blond, blue-eyed, rubicund child taught himself to read at the age of 3. He acquired a fantastic arithmetical skill and a pictorial memory by observing his father adding columns in his account books. In his future scientific work, he was especially fond of discovering relationships and laws from masses of data. At the age of 8, he entered the fifth grade of the cathedral school, where he distinguished himself particularly in physics and mathematics and from which he graduated, the youngest and ablest student, in 1876.

Theory of Electrolytes

Arrhenius entered the University of Uppsala, where he studied chemistry, physics, and mathematics. As he was not satisfied with his chief instructor in physics, he left Uppsala in 1881 to work on the conductivities of electrolytes at Stockholm under the physicist E. Edlund. In 1884 Arrhenius presented his results (Recherches sur la conductibilité galvanique des électrolytes) together with a new theory of electrolytes (Théorie chimique des électrolytes) in a 150-page dissertation for the doctorate at Uppsala. Although he compromised and moderated his radical ideas, his professors were not impressed and only grudgingly passed the dissertation.

Arrhenius's theory of electrolytes encountered widespread resistance from the scientific world, but it eventually found confirmation in the modern theory of atomic structure. Of the 56 theses advanced in his 1884 dissertation, only a few have not withstood the test of time or have had to be greatly modified. In order to explain the nonconductance of solid salt and pure water when tested separately and the conductance of an aqueous salt solution, Arrhenius postulated that when a solid salt is dissolved in water its molecules dissociate or ionize into charged particles, which Michael Faraday had called ions years before. Whereas Faraday assumed that such ions are produced only during electrolysis, Arrhenius proposed that they are already present in solution even without the application of an electric current. Chemical reactions in solutions are thus reactions between ions. Arrhenius's views were essentially correct for weak electrolytes (weak acids, bases, and other covalent substances), but for strong electrolytes his ideas were modified in 1923 by the Debye-Hückel theory of inter-ionic attraction.

Professional Recognition

With the aid of a travel grant from the Swedish Academy of Sciences, Arrhenius devoted his next few years to travel and study. He worked with Wilhelm Ostwald in Riga and Leipzig, with Friedrich Kohlrausch in Würzburg, with Ludwig Boltzmann in Graz, and with J. H. van't Hoff in Amsterdam.

In 1891 Arrhenius was appointed lecturer and in 1895, over strong objections, professor of physics at the Technical University of Stockholm, of which he became rector in 1896. During this time he courted and married Sofia Rudback. The couple had a son, Olav Vilhelm, who became a worker in soil science and agricultural botany. Three children were born of his second marriage, to Maria Johansson.

In 1901 Arrhenius was elected, with strong opposition, to th Swedish Academy of Sciences. The following year he received the Davy Medal of the Royal Society, and in 1903 he became the first Swede to receive the Nobel Prize in chemistry for his theory of electrolytic dissociation. He was appointed rector of the newly founded Nobel Institute for Physical Research at Stockholm in 1905, a position he held until his retirement in the spring of 1927.

Spectrum of Scientific Achievement

After his theory was accepted by the entire scientific world, Arrhenius turned his attention to other topics. He became interested in the widest application of the fundamental theory of chemical reactions. In 1902 he began to apply the laws of theoretical chemistry to physiological problems, especially those of serum therapy (immunochemistry). He found that organismic changes follow the same laws as ordinary chemical reactions and that no essential difference exists between reactions in the test tube and those in the human body.

Arrhenius became active in the fields of astronomy and cosmic physics, and he proposed a new theory of the birth of the solar system by the collision of stars. He used the ability of radiation pressure to transport cosmic material to explain comets, the corona, the aurora borealis, and zodiacal light. He also hypothesized that spores of living matter are transported by radiation pressure from planet to planet with the resultant spread of life throughout interstellar space. He developed a theory to explain the ice ages and other profound climatic changes undergone by the earth's surface. He reflected upon the world's supply of energy and the conservation of natural resources. He dreamed of a universal language and proposed a modified form of English. There was hardly a field of science to which he did not make original, if not universally accepted, contributions. During his last years he wrote several textbooks and many books of a popular nature, in which he made it a point to indicate what was still to be done in the fields under discussion. Arrhenius had a healthy constitution, but he made great demands upon himself in order to maintain his extraordinary productivity. After a brief attack of acute intestinal catarrh in September 1927, he died on October 2 and was buried in Uppsala.

Further Reading

The biography by Wilhelm Palmaer, "Svante Arrhenius, 1859-1927," originally in German, appears in an abridged translation in Eduard Farber, ed., Great Chemists (1961). A thumbnail sketch of Arrhenius and a brief evaluation of the electrolytic dissociation theory are contained in Eduard Farber, Nobel Prize Winners in Chemistry, 1901-1961 (1963). Benjamin Harrow, Eminent Chemists of Our Time (1920), explains how Arrhenius formulated his theory of electrolytic dissociation. A popularized summary of his life and work may be found in Bernard Jaffe, Crucibles: The Story of Chemistry, from Ancient Alchemy to Nuclear Fission (1930; rev. ed. 1948).

Additional Sources

Svante Arrenius, 1859-1927, Moskva: "Nauka," 1990.

Crawford, Elisabeth T., Arrhenius: from ionic theory to the greenhouse effect, Canton, Mass.: Science History Publications/ USA, 1996. □

Arrhenius, Svante

COFOUNDER OF MODERN PHYSICAL CHEMISTRY
1859–1927

Svante August Arrhenius, born in Vik, Sweden, is regarded as the cofounder of modern physical chemistry. For his theory of electrolytic dissociation, Arrhenius received the Nobel Prize in chemistry in 1903. He also made important contributions to chemical kinetics and many other branches of science.

In 1884 Arrhenius obtained his Ph.D. from the University of Uppsala with a thesis on the conductivities of electrolytic solutions. Although poorly rated by his examiners, his thesis attracted the attention of the most distinguished physicists and physical chemists in Europe at the time. Arrhenius collaborated with a number of them from 1886 until 1890. Based on his international reputation, he secured a post at the Technical High School in Stockholm, first as a lecturer, then as a professor, and finally as its rector. He later became director of the new physical chemistry institute of the Nobel Foundation in 1905. By that time, his interests had already shifted toward other fields of science.

Arrhenius is mainly known for his equation describing the temperature dependence of chemical reaction rates:

k = A exp(−E /RT )

with k being the reaction rate constant, A a preexponential factor, E the activation energy, R the gas constant, and T the absolute temperature. Although the equation was first formulated by Dutch physical chemist Jacobus Hendricus van't Hoff in 1884, Arrhenius provided the interpretation of it that is still in use today. He suggested that the crucial step in a chemical reaction was the formation of activated molecules from the reactant molecules and that both states were in equilibrium , separated from each other by the activation energy E. Accordingly, he explained the temperature dependence of the reaction rate as a change of equilibrium, such that with increasing temperature more activated molecules were formed to undergo reaction. Furthermore, plotting the experimental results of ln k against 1/T (the so-called Arrhenius plot) yielded in many cases a straight line, from the slope of which one could easily calculate the activation energy E.

Arrhenius's most famous contribution, making him with the German physical chemist Friedrich Wilhelm Ostwald and van't Hoff a cofounder of modern physical chemistry, was his theory of electrolytic dissociation. Electrolytes are substances such as salts, acids, and bases that conduct electric current in solutions. Arrhenius suggested that every electrolyte, once dissolved in a solvent like water, dissociated into oppositely charged ions to a certain degree that depended on its nature and overall concentration. Before this explanation, chemists had continued to believe that electrolytes dissolved as uncharged molecules that could be separated only by strong electric forces, such as in electrolysis. Although the forces for electrolytic dissociation remained unclear for some time, Arrhenius's assumption could explain a wide range of phenomena and laws beyond electrochemistry. This included Raoult's laws of vapor pressure lowering and freezing point depression, Ostwald's dilution law, and van't Hoff's law of osmotic pressure of solutions. As Ostwald later showed in his acid-base theory, it also provided a quantitative understanding of the chemical activities of electrolytes in solution.

In his later years, Arrhenius applied the concepts of physical chemistry and physics to many other branches of science, including biochemistry, geoand cosmic physics, and meteorology. In retrospect, his most remarkable contribution was perhaps his model of the greenhouse effect , according to which the temperature of Earth's lower atmosphere is determined by the concentration of carbon dioxide. Earth's surface, after being warmed by sunlight, emits energy in the form of infrared radiation, which is absorbed by molecules in the atmosphere, particularly carbon dioxide; the absorption of infrared radiation leads to heat. At that time, the greenhouse effect model was used to explain the glacial periods, rather than any climatic changes induced by the human production of carbon dioxide, as is the case today.

see also Global Warming; Ostwald, Friedrich Wilhelm; van't Hoff, Jacobus.

Joachim Schummer

Bibliography

Crawford, Elisabeth (1996). Arrhenius. From Ionic Theory to the Greenhouse Effect. Canton, MA: Science History Publications.

Snelders, H. A. M. (1970). "Arrhenius, Svante August." In Dictionary of Scientific Biography, Vol. I, ed. Charles C. Gillispie. New York: Scribner.