Abstract: According to the energy postulate, the general form of the chemical potential is educed separately from thermodynamics and non-equilibrium thermodynamics, and two examples are expatiated by the general form of the chemical potential. The results show that the general chemical potential not only expands the chemical potential definition of the classical thermodynamics and field of application, but also indicates the connotation of external physical fields＇ contribution to the chemical potential and effect on the chemical potential. When actual problems are analyzed by applying the general chemical potential, the right conclusion is resulted in by the general chemical potential, and the discussions on problems are simple and easily understood.

Key words: energy postulate, general chemical potential, phase equilibrium, critical radius