The award for chemistry was bestowed to him in honor of his theory of electrolytic dissociation, though in its incipient form, which appeared in his doctoral dissertation, the theory was poorly received by his professors. The barely passing grade that he was given for the dissertation did not discourage Arrhenius, however, and his persistence eventually led to the general acceptance of many of his ideas regarding electrolytes, acids, bases and chemical reactions.
Arrhenius showed early promise of success, learning to read at the age of 3 and acquiring a pronounced interest in mathematical calculations in his youth by observing the accounting practices of his father, a land surveyor for the University of Uppsala. When he was 8 he entered the local school, from which he graduated as the youngest and most advanced student in 1876. Subsequently he enrolled at the University of Uppsala, where he studied physics, mathematics and chemistry. In 1881, Arrhenius moved to Stockholm to study under Erik Edlund at the Physical Institute of the Swedish Academy of Sciences. There his studies soon came to focus upon electrolysis, which entails the use of an electric current to produce a chemical change in an electrolyte.
Electrolytes were not well understood at the time, electrolysis having only come into practice in the early 1800s. The great experimental physicist Michael Faraday had suggested that charged particles he termed ions were formed by the process of electrolysis, but Arrhenius’ work led him to a somewhat different conclusion: electrolytes contain ions even when they are not exposed to electricity. Based upon his investigations on the conductivity of electrolytes, Arrhenius was convinced that when an electrolyte is dissolved in water, it dissociates to some degree into positive and negative ions, and that the extent of dissociation depends upon the nature of the electrolyte and its level of concentration (dissociation being greater in dilute solutions). These ions Arrhenius considered responsible not only for carrying electric current, but also for the chemical reactions that occur in solutions. In the dissertation he submitted in 1884, Arrhenius presented an early form of his theory of electrolytic dissociation, but the preference for detailed experimentation and skepticism of his ideas among the faculty judging the work resulted in his receiving a bare pass.
Confident in the promise of his work, Arrhenius boldly sent copies of his dissertation to many prominent chemists around the world. One of these chemists, Wilhelm Ostwald of Germany, was so intrigued by the paper that he traveled to Uppsala to meet Arrhenius and offer him a job. Instead of taking the research position, however, Arrhenius accepted a lectureship in physical chemistry offered to him at Uppsala soon after Ostwald’s visit in order to stay closer to his father, who was in poor health. His father died in 1885, and in the following year Arrhenius was awarded a travel grant from the Swedish Academy, enabling him to journey to Riga to work with Ostwald, which he followed up with trips to Würzburg, Germany, Graz, Austria, and Amsterdam, The Netherlands, to study with Friedrich Kohlrausch, Ludwig Boltzmann, and J. H. van 't Hoff, respectively. Regular contact with such great scientists helped Arrhenius hone many of his ideas, and gradually his views began to win over adherents.
In close association with his theory of electrolytic dissociation, Arrhenius developed definitions of acids and bases that were the chief designations utilized for them for many years. According to Arrhenius, an acid is a substance that, when it dissociates in water, yields hydrogen ions (H+), whereas the dissociation of a base in water yields hydroxide ions (OH-). Notably, Arrhenius’ definitions fail to address the fact that water is not the only solvent in which substances may function as an acid or a base. Also, it was not realized at the time that hydrogen ions do not exist independently in solutions for long, but rather combine with water to form hydronium ions (H30+). Some of the shortcomings of the Arrhenius theory of acids and bases were addressed by later scientists. According to the Brönsted-Lowry theory, for instance, an acid is a proton donor and a base is a proton acceptor, definitions that do not make specific reference to water, as do the Arrhenius definitions.
Arrhenius also developed the concept of activation energy, which is the minimum energy necessary for a particular chemical reaction to transpire. He utilized this concept to explain why heat energy is often necessary to produce chemical reactions. His work in this area further resulted in the Arrhenius equation, which quantitatively expresses the relationship between the rate at which a reaction proceeds and the reaction’s activation energy.
Over time Arrhenius’ work in physical chemistry gained him significant renown. In 1891, he was offered a professorship in Germany but declined the offer. Instead he accepted an appointment at the Royal Institute of Technology in Stockholm, becoming a physics professor there in 1895 and rector the following year. The early twentieth century was a particularly triumphant time for Arrhenius, who was elected to the Swedish Academy of Sciences in 1901, bestowed the prestigious Davy Medal of the Royal Society of London in 1902, and the Nobel Prize in Chemistry in 1903. In 1905, Arrhenius was offered another professorship in Germany, but preferred to remain in Sweden, where he was given the directorship of the Nobel Institute of Physical Chemistry, a position established especially for him.
Once his main theories became widely accepted, Arrhenius embarked upon investigations of many other topics, including osmosis, immunology, astronomy, toxins and antitoxins, the origin of life and the effect of carbon dioxide levels on climate. He also composed a number of books, including theoretical chemistry, electrochemistry, and immunochemistry textbooks, a textbook on cosmic physics and several books intended for the general public on topics ranging from smallpox to the formation of planets. While carrying out these other projects, Arrhenius maintained his post at the Nobel Institute, only relinquishing it shortly before his illness-related death on October 2, 1927.