Water Vapor Pressure in the Presence of Air

The equilibrium between water and water vapor in the case of humid air is illustrated in Fig. 4.7. 

FIGURE 4.7 Equilibrium between water and vapor in the presence of air, 

2 STATE VALUES Of HUMID AIR MOLLIER DIAGRAMS AND THEIR APPLICATIONS 

The state of equilibrium differs from the equilibrium between water and pure water vapor in that, in a gas phase, there is also inert gas (dry air) present. This means that the water pressure is equal to the total gas pressure, p -- p, + ph, not to the water vapor pressure p, . 

In a state of equilibrium the chemical potentials of water and water vapor are equal  

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