Chemistry: 1934

Urey, Harold Clayton pronounced YOO ree, (1893-1981), was an American chemist who made important contributions in two main fields. During his early career, he conducted research on isotopes. Isotopes are atoms of the same element that differ in mass-that is, in the amount of matter they contain. Different isotopes of an element have the same number of protons but different numbers of neutrons in their nucleus. Urey's later work centered on the history and chemical nature of the solar system. During the late 1960's and early 1970's, he played a prominent role in the interpretation of lunar samples gathered by Apollo astronauts.

Urey won the 1934 Nobel Prize in chemistry for the discovery of deuterium, a rare isotope of hydrogen. During World War II (1939-1945), he directed a laboratory where isotopes of boron, hydrogen, and uranium were produced for use in the development of the atomic bomb. Urey's study of Earth and the solar system began after the war. He calculated the temperature of ancient oceans by determining the amount of certain isotopes in fossil shells. He also studied the chemical makeup of the sun, moon, and planets and formulated theories on the origin of the solar system.

Urey was born in Walkerton, Indiana, on April 29, 1893. He earned a Ph.D. degree from the University of California at Berkeley in 1923. He served on the faculty of Columbia University from 1929 to 1945, at the University of Chicago from 1945 to 1958, and at the University of California at San Diego from 1958 until his death on Jan. 5, 1981.

Contributor: Daniel J. Kevles, Ph.D., Professor of Humanities, California Institute of Technology.