The thermodynamic potentials also satisfy
where  is the chemical potential defined as (for constant n</sub> with j≠i):
This last partial derivative is the same as , the partial molar Gibbs free energy.  This means that the partial molar Gibbs free energy and the chemical potential, one of the most important properties in thermodynamics and chemistry, are the same quantity. Under isobaric (constant P) and isothermal (constant T ) conditions,  knowledge of the chemical potentials, , yields every property of the mixture as they completely determine the Gibbs free energy.