Lars Onsager
Onsager, Lars (1903-1976), a Norwegian-born American chemical physicist, was awarded the 1968 Nobel Prize in chemistry for developing a general theory of the thermodynamics of irreversible chemical processes. Thermodynamics is the study of various forms of energy and of the conversion of energy from one form into another. Onsager's theory has been unofficially called the fourth law of thermodynamics.
Onsager was the son of a barrister of the Supreme Court of Norway. He was taught at home and at a rural private school before graduating in 1920 from the Frogner School in Oslo. That fall he enrolled in the Norwegian Institute of Technology in Trondheim, where he studied chemical engineering.
In 1923, Dutch chemist Peter Joseph William Debye, a future Nobel laureate, and his German colleague Erich Hückel, proposed a theory of strong electrolytes, salts whose solutions are good conductors of electricity. The Debye-Hückel theory mathematically accounted for the electrical interactions of ions in solution. Onsager realized that the two scientists had failed to take into account the chaotic movement of all the ions in a solution, and he figured out a revised mathematical expression. While traveling in Denmark, Germany, and Switzerland in 1925, Onsager went to see Debye so he could tell him personally of the problem with his theory of electrolytes. Debye's response was to offer Onsager a research assistantship. After completing an appointment as resident scientist at the Norwegian Institute of Technology (1925—1926), Onsager moved to Zurich to work with Debye at the Federal Institute of Technology (1926-1928).
Onsager came to the United States in 1928 for a position at Johns Hopkins University, teaching freshman chemistry. His teaching debut was so unsuccessful that he was dismissed after a single semester. That spring he worked on his own on the research that would later earn him the Nobel Prize in Chemistry.
Onsager then joined the faculty at Brown University, where he spent five years. Onsager did much important research at Brown. Attempting to generalize his earlier work on the motion of ions in solution when exposed to an electrical field, he eventually derived the Law of Reciprocal Relations, a general mathematical expression about the behavior of substances in solution. After publishing a first version of the law in 1929, in 1931, Onsager submitted a more general form that appeared that year as a two-part article, “Reciprocal Relations in Irreversible Processes,” in the prestigious Physical Review. The value of Onsager's general theory of thermodynamics to chemistry, physics, biology, and technology was not recognized until a decade later, but since that time, the elegance of its formulation has led some scientists to refer to it as the fourth law of thermodynamics. At the 1968 Nobel Prize ceremony, it was cited as “one of the great advances in science during this century.”
During the 1930's, Onsager also wrote an article describing a correction to a formula that Debye had worked out for the dielectric constant of polar molecules. However, Debye refused to accept the article for publication in the journal of which he was an editor. The so-called Onsager formula was published in English in 1936, but many years passed before Debye accepted it.
Budgetary cutbacks at Brown during the Great Depression led to the elimination of Onsager's position in 1933. That year, he married Margarethe Arledter and accepted a Sterling postdoctoral fellowship at Yale University. In 1935, Yale awarded him a Ph.D. degree in chemistry. Onsager remained at Yale until 1972 and rose through the ranks to Josiah Willard Gibbs Professor of Theoretical Chemistry.
Since Onsager did not become a naturalized U.S. citizen until 1945, he could not do defense research during World War II (1939-1945). Instead he spent the war years analyzing whether statistical mechanics could provide a theoretical explanation for the phase changes of matter. Although many thought this physics problem insoluble, Onsager showed that the specific heat of a ferromagnetic system rises to infinity at the transition point. At the Nobel Prize award ceremony in 1968, the spokesman for the Royal Swedish Academy cited the significance of this piece of work for “making possible a theoretical treatment of phase changes.”
Onsager left Yale in 1971 when he reached 68, then Yale's official retirement age. In 1972, he accepted an appointment as distinguished university professor at the Center for Theoretical Studies at the University of Miami. He continued research there until his death of a heart attack in 1976.