Introduction

When a gas is in contact with a liquid, the gas receives vapor from the liquid until the partial pressure of the vapor in the gas mixture equals the vapor pressure of the liquid at the existing temperature. When the concentration of the vapor in the gas mixture reaches this equilibrium value, the gas is said to be saturated with the vapor.

If the partial pressure of the vapor in the gas mixture exceeds the vapor pressure of the liquid, condensation of the vapor takes place.