The active practice of medicine not being congenial to him, in 1836 he was appointed chemist to the geological survey of Pennsylvania being administered by his brother Henry.

There he remained until 1852, when he was called to succeed his brother James as professor of chemistry at the University of Pennsylvania, where he became dean of the medical faculty in 1856.

In 1877 he resigned these appointments to accept the professorship of chemistry and toxicology in Jefferson Medical College, which he then retained till 1884, when he was made professor emeritus.

During the American Civil War, he served as acting assistant surgeon at the West Philadelphia military hospital 1862–63.

He was a fellow of the College of Physicians and Surgeons, member of various scientific societies, one of the incorporators of the National Academy of Sciences, and president of the Franklin Institute 1875–79.