Collection contains materials relating to Joel Henry Hildebrand's professional activities as a professor and researcher, primarily from the latter part of his career. The correspondence includes interchanges with journals, professional organizations, and colleagues, many of whom were also personal friends. Documents pertaining to Hildebrand's professional activities represent the many awards and tributes he received during his long active retirement, including programs and correspondence from Hildebrand's milestone birthday celebrations. The collection includes drafts, notes, and reprints of many of Hildebrand's scientific papers, from his 1906 thesis to his last published work in 1981. His research on solubility and his interest in caisson sickness (the "bends") are both well represented. Hildebrand's writings for a general audience on science and scientists, as well as on education and other broader cultural topics, show his investment in issues beyond his chosen field of chemistry. The collection also contains a small amount of materials relating to Hildebrand's various administrative duties at the University of California, including his role in the loyalty oath controversy, as well as documents from his involvement in the Sierra Club.