Joel Henry Hildebrand (November 16, 1881 – April 30, 1983) was an American educator and a pioneer chemist. He was a major figure in chemistry research specializing in liquids and nonelectrolyte solutions.
Hildebrand graduated from the University of Pennsylvania in 1903. He served briefly in the faculty before going to the University of California, Berkeley as a chemistry instructor in 1907. Within five years he became an Assistant Professor. In 1918 he was elevated to Associate Professor before finally being granted Full Professorship a year later in 1919. He served as the Dean of the College of Chemistry from 1949 through 1951. He retired from full time teaching in 1952 but remained a University Professor at Berkeley until his death. Hildebrand Hall on the Berkeley campus is named for him.
Hildebrand served on the Council of the National Academy of Sciences and was also a member of the Citizens Advisory Committee on Education to the California Legislature. Hildebrand made several discoveries of which the most notable was the introduction in the mid-1920s of helium and oxygen breathing mixtures to replace air for divers to alleviate the condition known as the bends. He realized that the problem was caused by nitrogen gas dissolved in blood at high pressure, which was expelled too rapidly on return to the surface. Helium does not cause the same problem due to its much lower solubility in aqueous solutions such as blood. This discovery was later used to save the lives of 33 members of the submarine USS Squalus which went down in 1939.
Hildebrand won virtually every major prize in the field of chemistry except the Nobel Prize. The American Chemical Society created the Joel Henry Hildebrand Award in his honor for work pertaining to the field of theoretical and experimental chemistry of liquids. The first award was presented to Hildebrand himself in 1981 as part of the observances of his 100th birthday. The award is currently sponsored by Exxon Mobil.
Professor Hildebrand often said he most cherished his role as a teacher. In an interview conducted shortly before his 100th birthday, he observed: "Good teaching is primarily an art, and can neither be defined or standardized ... Good teachers are born and made; neither part of the process can be omitted." He remained committed to working with undergraduate students even at the age of 100. He came to his office on campus nearly every school day until declining health made it impossible.
Hildebrand was also active in the Sierra Club, serving as its president from 1937 through 1940. As a member he contributed to many important land-use reports about State and National Parks in California.