Estimation of Solute Concentration in Equilibrium
The molality of NaCl in the resulting droplet at a specific RH was calculated using Microsoft Excel’s solver tool according to an empirical relationship [25]:(3) where m is the molality of NaCl (mol (kg water)−1). The concentration of NaCl was then calculated based on m:(4) where Cs is the concentration of solute in equilibrium; Ms is the molecular weight of NaCl (58.44 g mol−1); vs is the molar volume of NaCl (2.7×10−2 L mol−1); and the number 1 in the denominator represents the volume of 1 kg of water, i.e., 1 L.