Studies of Evaporation of Small Drops

Abstract

The rates of evaporation of small droplets of diamyl sebecate (average radius R∼10^—4 cm) were measured in a Millikan oil‐drop chamber, and observed to obey a law of the form dR/dT = a/(1+bR) which has been predicted by the theories of Fuchs and Frisch and Collins. Using a nonequilibrium distribution function of the velocities, the relationship has been rederived in a more rigorous fashion (over a limited range of conditions). Certain corrections in the constants a and b are introduced, and the validity of the Fuchs theory in this range of conditions is demonstrated. Using the formulation of Frisch and Collins, the law may be derived in the same form, subject to certain approximations. An empirical form of the Stokes‐Cunningham law for the limiting velocity of fall in a dilute medium has been obtained for dicapryl sebecate in air.