Josiah Willard Gibbs (1839-1903) was an American mathematical physicist whose pioneer work in statistical mechanics laid the basis for the development of physical chemistry as a science.

When Josiah Willard Gibbs began his work, thermodynamics had become a true science, firmly based on recently formulated laws of the conservation of energy. These and energy and the law of the dissipation or degradation of energy (first and second laws of thermodynamics), which had been worked out mathematically.

Gibbs began with the known thermodynamic theory of homogeneous substances and worked out the theory of the thermodynamic properties of heterogeneous substances. It was this work which, some years later, provided the basic theory for the new branch of science known as physical chemistry. Gibbs's great contribution, "On the Equilibrium of Heterogeneous Substances," was published in the Transactions of the Connecticut Academy of Arts and Sciences in 1876 and 1878. Before the end of...