A Modified Rackett Equation Applied to Water and Aqueous NaCl and KCl Solutions

Abstract

The Rackett equation is modified for the calculations of the liquid volumes of H2O, H2O + NaCl (up to 25.0 NaCl mass %), and H2O + KCl (up to 4.0 KCl mass %) solutions under vapor-saturated conditions. Two terms are added to the index part of the Rackett equation for describing the volumetric property of liquid water. The average of the absolute deviations from the NBS/NRC Steam Tables at 293.15 K to 643.15 K in steps of 10 K becomes 0.39%. The effect of the dissolved salt on the volumetric property is included in the index part. The equations for molar volumes of aqueous NaCl solutions at 373.15 K to 773.15 K and aqueous KCl solutions at 373.15 K to 643.15 K are obtained on the basis of the previous experimental results. The average of the absolute deviations for aqueous NaCl solutions is 0.77%, and that for the aqueous KCl solutions is 0.63%.