Prediction of Electrolyte Solubilities from Minimal Thermodynamic Information

Summary.

 A method is proposed that permits the proper extrapolation of thermodynamic quantities represented by the Pitzer equations from 25°C to other temperatures. The new method, which assumes temperature independent heat capacities, was tested for the NaCl*H₂O system and found very satisfactory. A new evaluation of the Na₂CO₃*H₂O system according to the CALPHAD method is presented, and solubilities for the quaternary Na₂CO₃*NaCl*NaOH*H₂O and its ternary subsystems are predicted. Limitations of (i) these predictions and of (ii) the Pitzer model regarding extrapolations to high molalities are discussed.