Who developed the concept of chemical potential?

Josiah Willard Gibbs developed the concept of chemical potential. He introduced it in his 19th-century work on chemical and thermodynamic equilibrium as a quantity describing how a system’s energy changes when the amount of a chemical species changes.

In modern notation, the chemical potential of component i is commonly defined as μᵢ = (∂G/∂Nᵢ) at constant temperature, pressure, and fixed amounts of the other components. It is therefore the partial molar Gibbs free energy. Chemical species tend to move, react, or change phase in ways that lower the appropriate chemical-potential differences, just as heat flows down a temperature gradient.

Gibbs’s papers on the equilibrium of heterogeneous substances, published from 1874 to 1878, established much of the mathematical foundation of chemical thermodynamics. He connected chemical potential with phase equilibrium, reactions, mixtures, and the phase rule, F = C − P + 2.

The concept is sometimes confused with Gibbs free energy itself. Gibbs free energy is a property of an entire system, while chemical potential is its change per added amount of one component under specified conditions. In a mixture, each component has its own chemical potential.