Leo Schubert, 62, chairman of the chemistry department at American University for 25 years and then university professor since 1975, died Wednesday at Suburban Hospital in Bethesda after a heart attack.

Dr. Schubert joined the faculty of American University in 1951, when he was named department chairman. Since then he had directed a number of programs, including summer research participation programs for area high school students, and an institute for high school teachers of chemistry and physics.

He had been editor of the Journal of College Science Teaching since its founding in 1971.

A native of New York City, Dr. Schubert earned a bachelor's degree from the City College of New York, a master's degree from New York University, and a doctorate in chemistry from the University of Maryland.

He moved to this are in 1942 when he became a chemist with the National Bureau of Standards. He held that post until joining American University.

He was active in a number of professional organizations, including the American Chemical Society, where he served on a subcommittee for the education and employment of the disadvantaged, and the American Association for the Advancement of Science, where he served as secretary of the association's chemistry section from 1969 to 1977.

Dr. Schubert was a member of the Cosmos Club.

He is survived by his wife, Edith, of the home in Bethesda; a daughter, Leda, of Plainfield, Vt.; a brother, Uriel, and a sister, Shirley Winkler, both of White Plains, N.Y.