Concentrated aqueous electrolyte solutions: Analytical equations for humidity-concentration dependence

The Henry's law, Freundlich, and Dubinin-Astakhov, Brunauer-Emmett-Teller e quations, and a new modification of the BET equation are used for the therm odynamic analysis of the activity of water over wide ranges of temperature (260-600 K) and water content (mole fraction 0.3-0.8) in concentrated aqueo us solutions of electrolytes. The solutes considered are H2SO4, CaCl2, LiBr , LiCl, LiI, MgCl2, and NaOH in bulk solutions, and CaCl2 and LiBr disperse d in porous matrixes. The generalized Henry's law equation is found to affo rd a correct extrapolation of bulk solution properties measured at low and moderate salt concentrations to the region of low water content. The sugges ted modification of the BET equation as well as the Dubinin-Astakhov equati on give an accurate (relative error less than 1%) description of literature data on the humidity-concentration dependence and can be used for the reli able prediction of this dependence in the region of intermediate conditions .