THE STABILITY OF LIQUID EVAPORATION EQUILIBRIUM

For the evaporation of the pure liquid under the condition of constant temperature and constant external pressure, the phase equilibrium of the liquid vapor in the bubble and the liquid outside the bubble is always a kind of stable equilibrium whether there is air or not in the bubble. If there is no air in the bubble, the bubble and liquid cannot coexist in the mechanical equilibrium when the vapor pressure of the liquid in the bubble is less than or equal to the external pressure; the bubble and liquid can coexist in an unstable equilibrium of mechanics when the vapor pressure of the liquid is greater than the external pressure. If there is air in the bubble, the bubble and liquid can coexist in a stable equilibrium of mechanics when the vapor pressure of the liquid is less than or equal to the external pressure; the bubble and liquid can coexist in a stable and an unstable equilibrium of mechanics when the vapor pressure of the liquid is greater than the external pressure and less than a certain pressure pm; the bubble and liquid cannot coexist in the mechanical equilibrium when the vapor pressure of the liquid is equal to or greater than pm.