Gibbs, Josiah Willard (1839–1903)
Josiah Gibbs was a US theoretical physicist and chemist best known for his pioneering work in chemical thermodynamics. While a professor at Yale, he devoted himself to establishing the basics of physical chemistry. In On the Equilibrium of Heterogeneous Substances (2 vols, 1876 and 1878) he stated Gibbs' phase rule (see phase equilibria). The quantity known as Gibbs free energy is named after him. Gibbs also made fundamental contributions to the subject of vector analysis.