The entire phase diagrams of the ternary systems NaCl + NH4Cl + H2O, KCl + NH4Cl + H2O, NaCl +
AlCl3 + H2O, and KCl + AlCl3 + H2O, as well as the solubilities of sodium and potassium chlorides in
aqueous solutions of lithium chloride, were determined at T = (298 to 333) K. Additionally, the equilibrium
concentrations of pure ammonium chloride, lithium chloride monohydrate salt, and aluminum chloride-6-hydrate were also measured over the same range of temperatures. The measured data were correlated
as a function of temperature and content of the secondary electrolyte in the solvent by a least-squares
method. The proposed empirical equations of fit allow fair agreement between calculated and experimental
data, the invariant composition mixtures included, with standard deviations of fit to molality ranging
from ±(0.02 to 0.05) mol·kg-1. In concentrated solutions of lithium and aluminum chlorides, the
equilibrium concentrations of NaCl and KCl become very small. Therefore, because of the form of the
optimization criterion chosen for the fit, the relative deviations between the two sets of data increase
directly with the content of the secondary electrolyte.
Binary and ternary solubility data were measured for the NaCl-KCl-H,O system in the temperature range 293-360 K using a standard visual method. The solid-liquid phase diagram of the ternary system was calculated from the binary data and from the activity coefficients of the electrolytes evaluated by the Pitzer model. Some empirical functions of temperature were used to describe the virial coefficients. The calculated ternary solubilities were compared with the experimental values yielding a very good agreement. Therefore, it was possible to conclude that, in the range of concentration and temperature studied, the Pitzer model provides an excellent representation of the activity coefficients, thus allowing the accurate prediction of solubilities in the ternary system.
Des mesures de la solubilitk des sels dans les solutions binaires et ternaires du systkme NaCI-KCI-H,O ont ete effec-tukes h des temperatures entre 293 et 360 K, par une procedure visuelle. Le diagramme de phases solide-liquide pour le systkme ternaire a Ct C calcult en utilisant les donnCes de solubilite binaire et le modkle de Pitzer pour obtenir les coefficients d'activitk. Pour dkterminer les coefficients du viriel on a employe des fonctions empiriques de la temperature. Les predictions du modkle thermodynamique sont en trks bon accord avec les rtsultats obtenus experimentalement. On montre ainsi que, dans les gammes de composition et temperature etudiees, la mCthode de Pitzer donne une excellente estimation sur les coefficients d'activitk ce qui permets une prediction trks sfire des solubilites dans ce systkme ternaire.
The solubilities of sodium chloride in water + ethanol mixtures and of sodium and potassium chlorides
in systems of NaCl + KCl + water + ethanol were determined from (298 to 323) K and up to 20 mass %
alcohol in the solvent. An empirical fit of the measured data enabled the calculation of the solubility of
NaCl in water + ethanol mixtures as a function of temperature and alcohol content with an average
deviation of 0.1 mass %. Solubility data in the quaternary systems were correlated using an algorithm
that makes use of the Pitzer mole fraction-based equations for the activity coefficients of the electrolytes.
The parameters for the activity coefficient equations, taken from the literature, allowed fair agreement
between calculated and experimental solubilities in the NaCl field. However, in the KCl domain the
deviations were somewhat biased. A better fit of the entire set of solubilities was obtained by revising
the value of the short-range interaction parameter Q
ethanol,NaCl,KCl. After this tuning, the algorithm
reproduces the experimental solubility data of both salts with a standard deviation of ±0.023 mol·kgsolvent
-1.
The maximum differences between the experimental and calculated contents of sodium and potassium
chlorides in the invariant composition mixtures are 1.2% and 3.5%, respectively.
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