DETERMINATION OF VAPOR-PRESSURE FROM DROPLET EVAPORATION KINETICS

Evaporation kinetics of suspended single droplets are investigated in the temperature range 20 to 55°C, using Mie resonance spectroscopy. Experiments are carried out with a single-component organic droplet electrodynamically suspended either in a flowing N2 gas or in a vacuum, depending upon the volatility of the organic compound. A data analysis method is developed, which produces a best-fit empirical correlation in the form. 1n p= A+ B T+C 1n T+DTk,. that is valid over a temperature range spanning up to 9 decades on the vapor pressure scale. No estimate of the actual value of either the diffusivity or the evaporation coefficient is needed. This is accomplished by combining the high-temperature vapor pressure data available in the literature with the droplet evaporation rates measured in this work at lower temperatures. Results presented here for methanesulfonic acid, glycerol, oleic acid, and dioctyl phthalate clearly demonstrate the usefulness of the technique for ultra-low vapor pressure determinations. © 1991.