The activities of potassium chloride and of water in Dead Sea brine

The activities of KCl and of H₂O in Dead Sea water were estimated according to several approaches dealing with multicomponent electrolyte solutions. The activity of H₂O, both measured directly via its vapor pressure and calculated theoretically, is 0.754 ± 0.004 for brine of density 1.207 ± 0.003gcm^?3 at 25°C. The mean ionic activity of KCl in this brine ranges from 0.876 to 1.199 according to various treatments. These correspond to binary aqueous solutions 8.6–12.1 times richer than the brine. The brine cannot be simultaneously in equilibrium with respect to both H₂O and KCl with such binary solutions, so a hypothetically perfect semipermeable membrane cannot lead to a state of equilibrium between the brine and aqueous KCl of any concentration.