Calculation of Relative Humidity in Equilibrium with Strong Electrolyte Solutions by Thermodynamic Data

摘要

To estimate concentrations of electrolyte layers formed on metal surface in atmospheric environment, relative humidity (RH) in equilibrium with various concentrations of strong electrolyte solutions were calculated with available thermodynamic data. The activity coefficient of water (f_(H_2O)(X)) for the solution with molar fraction of water (X) could be given as a function of ionic strength of the solution, which was determined by mean activity coefficients data in literatures for electrolytes in the solution. RH values obtained as RH [percent] = 100 X f_(H_2O)(X) centre dot X were fitted well with measured values in literatures not only for solutions with individual electrolytes, for example NaCl or MgCl_2, but also for solutions with mixed electrolytes, for example sea salt.