Harold Clayton Urey

UXL Newsmakers, (2005)

Harold Clayton Urey

The American Scientist Harold Clayton Urey (1893-1981) received the Nobel Prize for chemistry in 1934 for his discovery of deuterium, the isotope of heavy hydrogen.

Harold Clayton Urey was born on April 29, 1893, in Walkerton, Ind., the son of Samuel Clayton Urey and Cora Rebecca Reinoehl Urey. After graduation from high school at 18, followed by some three months of education training at Earlham College, Harold taught in small country schools in Indiana and then Montana, where the family had moved. In 1914 he entered Montana State University (Bozeman) and graduated in three years with a baccalaureate in science.

The United States entered World War I in 1916 and Urey began work at the Barrett Chemical Company in Frankford near Philadelphia, preparing toluene for the production of TNT (trinitrotoluene) in 1917. In 1919 he returned to Montana to teach in the department of chemistry for 2 years. In 1921 he entered the graduate school at the University of California, Berkeley. Urey's interest focused upon molecular structure, a new field for scientists in the United States. His doctoral research on the conductivity of cesium vapor led him to the theory of thermal ionization in stellar atmospheres. Within two years he received the doctorate (1923) and, with a Scandinavian Foundation fellowship, later studied in Copenhagen at the Institute of Theoretical Physics, headed by Niels Bohr.

During his residence at Berkeley and Copenhagen, Urey began to work with some of the most prominent physicists and chemists of the 20th century, including Werner Heisenberg, Wolfgang Pauli and Georg von Hevsey. In Hamburg, Germany, he met he met Albert Einstein and James Franck, both of whom became his lifelong friends. In 1924 he returned to the United States to take a National Research Council fellowship at Harvard but instead accepted a faculty position as associate in chemistry at Johns Hopkins University, where he remained until 1929. There he and Russel Bichowsky hypothesized the idea of electron spin to explain the fine structure of the atomic spectral lines.

Between 1923 and 1929, Urey published 20 scientific papers or notes, almost all of them on aspects of atomic structure and the others on molecular band spectroscopy. In 1930 the book Atoms, Molecules, and Quanta, by A. E. Ruark and Urey, appeared. It became, and remained for a long time, one of the standard texts on the subject. Urey also published The Planets: Their Origins and Development in 1952.

While at Johns Hopkins, Urey married Frieda Daum in 1926. Her intelligence, good humor and warm hospitality made the Urey house a meeting place for scientists and intellectuals of all fields. As a tribute to her, the University of California at San Diego named its first large building the Harold and Frieda Urey Hall. The Ureys had four children: Gertrude, Elizabeth, Frieda Rebecca, Mary Alice and John Clayton.

In 1929 Urey became associate professor of chemistry at Columbia University in New York and professor in 1934. He refined his interest in sub-atomic and molecular structure and discovered a discrepancy in the atomic weight of hydrogen compared with that of oxygen, as measured by chemical means and by mass spectrometry. The discrepancy led to his identification of a heavy isotope of hydrogen (deuterium) found in concentrations of about 1 part per 5, 000. Calculating that the heavy isotope would boil less easily than the lighter, he had a friend at the Bureau of Standards, Ferinand G. Brickwedde, distill hydrogen. In the residue they and George M. Murphy discovered heavy water, molecules with one atom of oxygen and two atoms of hydrogen or deuterium. This led to Urey's award of the Nobel Prize for Chemistry in 1934.

Journal of Chemical Physics, published by the American Institute of Physics for the new breed of physical chemists interested in subatomic and molecular spectroscopy and structure. He remained editor until 1941, established the journal's preeminent reputation and the name of the field, chemical physics.

Urey's scientific work at Columbia became more and more concerned with the separation of isotopes of the lighter elements. The rarer isotopes of oxygen, nitrogen, carbon, and sulfur were concentrated. When full-scale work began at Columbia on the separation of the rare fissionable lighter isotope of uranium, U 235 , from the much more abundant U 238 , Urey became project head.

He then served as one of three program chiefs of the Manhattan Project. Even after the project's successful conclusion at Oak Ridge, Tennessee, he felt discouraged. The atmosphere of secrecy, the tight time schedule, and the limitations and conflicts of the work oppressed him.

After the war Urey, along with many others, was attracted to the plan of Chancellor Hutchins to build a group of research institutes at the University of Chicago. When the new institutes were founded, Urey was in the Institute for Nuclear Studies, later to become the Enrico Fermi Institute. For a while Urey, uncharacteristically, still suffering from the trauma of the war work, tended to drift, and he looked for new fields to conquer. He soon became interested in the past history of the earth and the planetary system. He initiated the use of analysis of the isotopic abundance in sea fossils to estimate the temperature of past oceans and helped prepare the most commonly accepted table of the elements. He also worked on meteoritic ages, composition, and classification. But his abiding interest then became earth's moon: Many of his later papers concerned the possible character of its formation and past history. He influenced astronomers and others to consider chemical evidence in the origin of the solar system and later became an active consultant to NASA, Lunar Sciences, and to the Space Science Board, National Academy of Sciences.