The Saykally Group

Experimental and Theoretical Physical Chemistry

Water Evaporation

The rates of water evaporation and condensation govern the growth, size distribution, and number concentration of cloud droplets, yet the details of these fundamental processes remain poorly understood. In this work, the effects of surface-active organic compounds on the evaporation rate of water are studied using a liquid microjet technique. Preliminary studies showed that acetic acid did not appreciable alter the evaporation kinetics.

Duffey, K. C. et al. Evaporation kinetics of aqueous acetic acid droplets: effects of soluble organic aerosol components on the mechanism of water evaporation. Phys. Chem. Chem. Phys. 15, 11634 (2013).

However, we recently observed a dramatic change in the evaporation coefficient, 0.24 ± 0.04, for 1 M HCl compared to the coefficient for pure water, 0.62 ± 0.09. Even more surprisingly was that measured evaporation coefficient for 0.1 M HCl, was 0.91 ± 0.08. These results suggest a large perturbation in the surface structure induced by either hydronium ions adsorbing to the water surface or by the presence of a Cl- ··· H3O+ ion-pair moiety in the interfacial region. Further studies are planned to test this hypothesis.

Rizzuto, A. M., Cheng, E. S., Lam, R. K. & Saykally, R. J. Surprising Effects of Hydrochloric Acid on the Water Evaporation Coefficient Observed by Raman Thermometry. J. Phys. Chem. C 121, 4420–4425 (2017).