THERMODYNAMICS OF AQUEOUS NAOH OVER THE COMPLETE COMPOSITION RANGE AND TO 523-K AND 400-MPA

The thermodynamic properties of aqueous NaOH are represented for the e ntire range to extremely high concentration by mole fraction based equ ations. The apparent molar volume and the solvent and solute activitie s are obtained from literature values based on experimental measuremen ts extending over the ranges 273-523 K and 0-400 MPa. For the range be low 6 mol kg(-1) the values from the very comprehensive treatment of S imonson et al. are given high weight. At the highest temperature the d issociated mole fraction of NaOH extends to 0.9. The equations represe nt the data satisfactorily over this very wide range and are of a form readily extended to more complex mixed systems and to solubility calc ulations.