Page "Vapor pressure" Paragraph 4

Experimental measurement of vapor pressure is a simple procedure for common pressures between 1 and 200 kPa.

Most accurate results are obtained near the boiling point of substances and large errors result for measurements smaller than.

Procedures often consist of purifying the test substance, isolating it in a container, evacuating any foreign gas, then measuring the equilibrium pressure of the gaseous phase of the substance in the container at different temperatures.

Better accuracy is achieved when care is taken to ensure that the entire substance and its vapor are at the prescribed temperature.

This is often done, as with the use of an isoteniscope, by submerging the containment area in a liquid bath.