William Draper Harkins

William Draper Harkins (December 28, 1873 – March 7, 1951) was an American physical chemist, noted for his contributions to surface chemistry and nuclear chemistry. He is also recognized now as one of the first environmental chemists. Harkins researched the structure of the atomic nucleus and was the first to propose the principle of nuclear fusion, four years before Jean Baptiste Perrin published his theory in 1919-20. His findings enabled, among other things, the development of the H-bomb. As a visiting professor with Fritz Haber in 1909, he was introduced to the study of surface tension, and he began work on the theory of solutions and solubility during a visit to MIT in 1909-1910.

Harkins was born in Titusville, Pennsylvania, and graduated with a PhD from Stanford University in 1907. He subsequently taught chemistry at the University of Montana from 1900 to 1912, and then spent the rest of his career at the University of Chicago.

Harkins correctly predicted the existence of the neutron in 1920 (as a proton–electron complex) and was the first to use the word "neutron" in connection with the atomic nucleus. The neutron was detected experimentally by James Chadwick in 1932. In the beginning of the 1930s, Harkins constructed the second ever cyclotron with fellow University of Chicago scientist Robert James Moon, improving greatly on the design of the previous one. From experiments with this, he concluded that the sun might be powered by nuclear fusion. Among other University of Chicago scientists who made use of this cyclotron was Enrico Fermi, who performed neutron diffusion experiments. Since 1978, the magnet yoke of the cyclotron Harkins built has been on display at Fermilab. Harkins was elected to the United States National Academy of Sciences in 1921 and the American Philosophical Society in 1925.

Among his students were Robert Mulliken, Lyle Benjamin Borst, Calvin Souther Fuller, Martin Kamen, Henry W. Newson, Samuel Allison, and Robert James Moon, Jr. (1911–1989).

Harkins died in Chicago. He is buried at Oak Woods Cemetery.