“…When near-equilibrium conditions are maintained, water activities and deliquescence points of various salts can be measured readily (Cohen et al, 1987a,b,c;Tang and Munkelwitz, 1978Andrews and Larson, 1993). With appropriate precautions, some time-dependent phenomena can also be investigated, such as chemical reactions (Ray et al, 1991;Rassat and Davis, 1992;Foss and Davis, 1994) and droplet growth or evaporation rates (Rube1 and Gentry, 1984;Davis and Ray, 1980;Sageev et al, 1986;Fung et al, 1987;Tang and Munkelwitz, 1991b). The diversity of successful studies attests to the strength of the trapped-particle technique.…”