Svante August Arrhenius (February 19, 1859-October 2, 1927) was a Swedish scientist working on the border between physics and chemistry. Though sometimes classed as a physicist and sometimes as a chemist, he is best described as one of the founders of the science of physical chemistry.
Arrhenius was born at Vik (also spelled Wik or Wijk), Kalmar district, near Uppsala, Sweden, the son of Svante Gustav and Carolina Thunberg Arrhenius. His father had been a land surveyor at the University of Uppsala, moving up to a supervisory position. At the age of three, Arrhenius taught himself to read, despite his parents' wishes, and by watching his father's addition of numbers in his account books, became an arithmetical prodigy.
In later life, Arrhenius enjoyed using masses of data to discover mathematical relationships and laws. At age 8, he entered the local cathedral school, starting in the fifth grade, distinguishing himself in physics and mathematics, and graduating as the youngest and ablest student in 1876.
At the University of Uppsala, he was unsatisfied with the chief instructor of physics and the only faculty member who could have supervised him in chemistry, so he left to study at the Physical Institute of the Swedish Academy of Sciences in Stockholm under the physicist Erik Edlund in 1881. His work specialized on the conductivities of electrolytes. In 1884, based on this work, he submitted a 150-page dissertation on electrolytic conductivity to Uppsala for the doctorate. It did not impress the professors, and he received the lowest possible passing grade. Later this very work would earn him the Nobel Prize in Chemistry.
There were 56 theses put forth in the 1884 dissertation, and most would still be accepted today unchanged or with minor modifications. The most important idea in the dissertation was his explanation of the fact that neither pure salts nor pure water conducts electricity, but solutions of salts in water do.
Arrhenius' explanation was that in forming a solution, the salt dissociates into charged particles (which Michael Faraday had given the name ions many years earlier). Faraday's belief had been that ions were produced in the process of electrolysis; Arrhenius proposed that, even in the absence of an electric current, solutions of salts contained ions. He thus proposed that chemical reactions in solution were reactions between ions. For weak electrolytes this is still believed the case, but modifications (by Peter J. W. Debye and Erich Hückel) were found necessary to account for the behavior of strong electrolytes.
The dissertation was not very impressive to the professors at Uppsala, but Arrhenius sent it to a number of scientists in Europe who were developing the new science of physical chemistry, such as Rudolf Clausius, Wilhelm Ostwald, and J. H. van 't Hoff. They were far more impressed, and Ostwald even came to Uppsala to persuade Arrhenius to join his research team. Arrhenius declined, however, as he preferred to stay in Sweden for a while (his father was very ill and would die in 1885) and had gotten an appointment at Uppsala.
Arrhenius next received a travel grant from the Swedish Academy of Sciences, which enabled him to study with Ostwald in Riga (now in Latvia), with Friedrich Kohlrausch in Würzburg, Germany, with Ludwig Boltzmann in Graz, Austria, and with van 't Hoff in Amsterdam.
In 1889 Arrhenius explained the fact that most reactions require added heat energy to proceed by formulating the concept of activation energy, an energy barrier that must be overcome before two molecules will react. The Arrhenius equation gives the quantitative basis of the relationship between the activation energy and the rate at which a reaction proceeds.
He developed a theory to explain the ice ages, and first formulated the idea that changes in the levels of carbon dioxide in the atmosphere could substantially alter the surface temperature through the greenhouse effect ("On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground", Philosophical Magazine 41: 237-76).
In 1901 Arrhenius was elected to the Swedish Academy of Sciences, against strong opposition. In 1903 he became the first Swede to be awarded the Nobel Prize in chemistry. In 1905, upon the founding of the Nobel Institute for Physical Research at Stockholm, he was appointed rector of the institute, the position where he remained until retirement in 1927.
Eventually, Arrhenius' theories became generally accepted and he turned to other scientific topics. In 1902 he began to investigate physiological problems in terms of chemical theory. He determined that reactions in living organisms and in the test tube followed the same laws. He also turned his attention to astronomy and cosmic physics, accounting for the birth of the solar system by interstellar collision. He considered radiation pressure as accounting for comets, the solar corona, the aurora borealis, and zodiacal light.
He thought life might have been carried from planet to planet by the transport of spores, the theory now known as panspermia. He thought of the idea of a universal language, proposing a modification of the English language.
In his last years he wrote both textbooks and popular books, trying to emphasize the need for further work on the topics he discussed.
See also: List of Swedish scientists