Joel Henry Hildebrand (November 16, 1881 – April 30, 1983) was an American educator and a pioneer chemist. He was a major figure in physical chemistry research specializing in liquids and nonelectrolyte solutions. Education and professorship He was born in Camden, New Jersey on November 16, 1881. 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 1913. Within five years he became an assistant professor. In 1918 he was elevated to associate professor before finally being granted full professorship in 1919. On August 4, 1919, he was shot and wounded by a chemistry assistant angry at not being recommended for further advancement. He was the dean of the College of Chemistry from 1949 through 1951 and retired from full-time teaching in 1952. Hildebrand Hall on the Berkeley campus is named for him. Accomplishments, discoveries, honors His 1924 monograph on the solubility of non-electrolytes, Solubility, was the classic reference for almost half a century. In 1927, Hildebrand coined the term "regular solution" (to be contrasted with "ideal solution") and discussed their thermodynamic aspects in 1929. A regular solution is one involving no entropy change when a small amount of one of its components is transferred to it from an ideal solution of the same composition, the total volume remaining unchanged. Hildebrand's many scientific papers and chemistry texts include An Introduction to Molecular Kinetic Theory (1963) and Viscosity and Diffusivity (1977). He received the Distinguished Service Medal in 1918 and the King's Medal (British) in 1948. Hildebrand served on the council of the National Academy of Sciences, of which he was a member, and was also a member of the Citizens Advisory Committee on Education to the California Legislature. He was elected to the American Philosophical Society in 1951. 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