Svante Arrhenius

Originator of Electrolytic Dissociation Theory

Arrhenius was born on February 19, 1859, in Vik, Sweden. After excelling in primary and secondary school, he entered the University of Uppsala in 1876 and concentrated on chemistry, physics, and mathematics, He began graduate studies at Uppsala, but transferred in 1881 to the Physical Institute of the Swedish Academy of Sciences, Stockholm, to finish his doctoral research.

Focusing his studies on the electrical conductivity of solutions, Arrhenius began to construct what would become the electrolytic dissociation theory. His theory attempted to explain observed changes in osmotic pressure, vapor pressure, and boiling and freezing points of solutions at various concentrations. He started from the premise that a solution of sodium chloride (salt) dissolved in water conducts an electrical current, but neither pure water nor dry salt does. Arrhenius postulated that when molecules of salt dissolve in water, they break apart, or dissociate, into smaller charged particles (now known as ions).

In 1884 Arrhenius submitted his thesis, which contained the basic principles of electrolytic dissociation theory. His doctoral committee was skeptical of his ideas, questioning in particular that electrically charged particles could exist in water. He was awarded a Ph.D. but given the lowest passing grade.

Arrhenius had his thesis printed and sent to numerous scientists in Germany and the Netherlands who were working on similar problems in the realm of physical chemistry. This group welcomed the electrolytic dissociation theory, and he was offered a job in Germany. Preferring to stay in Sweden, he accepted a lectureship at the University of Uppsala. He stayed only a brief time, though, as he was awarded a traveling scholarship in 1886 to visit the major scientific laboratories throughout continental Europe.

Arrhenius was honored with the Nobel Prize for Chemistry in 1903 for his work on the dissociation of electrolytes. Two years later, he became director of the physical chemistry division at the Swedish Academy of Sciences.

In his later years, Arrhenius’s interests broadened. He applied the principles of physical chemistry to biological phenomena, and he theorized that life forms might be transmitted from planet to planet by tiny spores. He also was among the first to postulate the greenhouse effect, which states that carbon dioxide in the atmosphere traps heat radiated from Earth’s surface. He hypothesized that reduction in the percentage of carbon dioxide in air caused the ice ages. Arrhenius died on October 2, 1927, in Stockholm, Sweden.

Svante Arrhenius’s Legacy

The electrolytic dissociation theory was Arrhenius’s major scientific contribution. By 1900 the theory had become widely accepted. Further research expanded the theory to include the following principles of electrolytic solutions: dissociation of the solute into free ions takes place even when no current is passed through the solution; conductivity depends on the number and migratory speed of the ions present; in weak electrolytes, degree of dissociation is directly proportional to degree of dilution; and in strong electrolytes, the ions impede each other’s migration through the solution, preventing complete dissociation.

The understanding of electrolytic solutions that grew out of Arrhenius’s theory paved the way for research into the properties of conductivity and the behavior of ions in solution. This research encompassed investigations of chemical equilibrium (the state of a chemical reaction where the net change in amounts of reactants stabilizes), semi­permeable membranes, osmotic pressure, corrosion, pH measurements, and ion concentration of fluids. Studies of the last were applied to medical problems such as determining the concentration of particular ions in blood.

Several technological developments emerged from the theory of electrolytic dissociation as well. Acid­base batteries were improved and fuel cells were devised. Protection against corrosion became possible with the development of thin ­layer electroplating on exposed metal surfaces. In addition, numerous industrial reactions were made possible or more efficient by the increased understanding of chemical kinetics (study of chemical reaction rates).

Svante Arrhenius – 1859­-1927