Single-component condensed matter at standard pressure can coexist with a gas with the same composition in equilibrium. Pressure of this gas is different from the total pressure and unique according to physical and chemical conditions of a condensed matter. It is called "equilibrium vapor pressure" here. In this note, an equilibrium vapor pressure of a condensed matter with a single-component of A at standard pressure is written as PA*∅. Note that “*” and "∅" indicate a quantity of a pure phase and ambient pressure, respectively. Eq. (3) in the page "G change of an ideal gas with P", molar Gibbs energy of this gas at a given temperature T is given as:
Since these condensed matter and gas are in equilibrium, their chemical potentials of component A are equal. Therefore,
where μcond,A* is the chemical component of a condensed matter with a single component A.