Vapour pressure of ammonium chloride aerosol: Effect of temperature and humidity

Abstract

The effect of relative humidity (RH) on the constant for dissociation of ammonium chloride into gaseous HCl and NH3 has been estimated for different temperatures, using thermodynamic data. At RH over 75-85% the ammonium chloride aerosol exists in the liquid phase, with the dissociation constant two orders of magnitude lower at 98% RH than for solid aerosol at the same temperature. It is predicted that ammonium chloride aqueous aerosol forms predominantly in fogwater and cloud droplets, and in regions where local emissions of NH3 are important. © 1987.