Evaporation rates of pure liquids measured using a gravimetric technique

We describe a gravimetric method for the determination of evaporation rates. The liquid sample is held in a partially filled, cylindrical open-topped tube within a vertically flowing gas stream. A simple model appropriate to this geometry is found to account for the variation of rate with liquid height within the sample tube and gas flow rate. Evaporation rates for a range of pure liquids with vapour pressures ranging from 0.1 to 500 Torr were determined and showed reasonable agreement with theoretical values estimated using literature values of the vapour pressures and vapour di†usion coefficients in air.