Dr. Sprague Coolidge, noted Harvard University chemist, musician and pioneer civil libertarian, died Wednesday at a nursing home in Concord, Mass. He was 83.

Dr. Coolidge, whose work in the field of physical chemisty was researched in the laboratories at Harvard, made a major contribution to scientific knowledge in 1933. He and a graduate student, using a new physics theory known as quantum mechanics, were able to calculate with precision the forces that hold atoms together in molecules.

Born in Chicago, Dr. Coolidge graduated from Harvard summa cum laude and received his Ph. D. degree in chemistry at Harvard in 1926.

In addition to his professional career as a chemist, Dr. Coolidge was an ardent political activist who helped found Americans for Democratic Action and in the 1920s and 1930s ran for several offices as a member of the Socialist Party.

During World War II, Dr. Coolidge worked for the Chemical Warfare Service here, helping to develop the charcoal used in gas masks. He was a member of the Harvard faculty from 1922 until his retirement in 1960.

When not involved in chemistry research or politics, Dr. Coolidge pursued such hobbies as music, photography and model railroads. He played the viola and oboe and published a book about building a model railway.

Dr. Coolidge is survived by his wife, Margaret, of the home in Cambridge; two sons, Frederic S. Coolidge of Tamworth, N.H., and Dr. John C. Coolidge of Cambridge; two daughters, Margaret C. Seeger, of Avondale, Colo and Elizabeth C. Winship, the wife of Boston Globe editor Thomas Winship: 15 grandchildren and eight great-grandchildren.