The Vapor Pressure of Dry Air at Low Temperatures

Abstract

Dry air is a mixture of gases (chiefly oxygen and nitrogen) having different boiling points. There is no single vapor-pressure curve, as in the case of a pure substance. Instead, the liquid-vapor equilibrium is represented by a bubble-point curve and a dew-point curve. The bubble-point pressure of a liquid mixture is that pressure at which, for a given temperature, vapor just begins to appear. When this pressure is plotted against temperature for a liquid mixture of constant composition, the curve obtained is called the bubble-point curve. The dew-point pressure of a gaseous mixture is that pressure at which, for a given temperature, liquid just begins to appear. When this pressure is plotted against temperature for a gaseous mixture of constant composition, the curve obtained is called the dew-point curve.