“…Though numerous experimental and theoretical investigations have been reported on binaries {NaCl + H 2 O} (see for example, Clarke and Glew 6 ) and {Na 2 SO4 + H 2 O} (see, for example, Marliacy et al 7 and references therein), much less data exists on the {NaCl + Na 2 SO 4 + H 2 O} ternaries. Thus, Tischenko et al 8 made measurements of mean activity coefficients of NaCl and Na 2 SO 4 in water at various composition between 278 and 318 K. However, most VLE data on this system were reported at 298 K; the reports concern the determination of osmotic coefficients by isopiestic methods (Robinson et al, 9 Platford, 10 and Wu et al 11 ) or the direct measurements of activity coefficients from electrochemical techniques (Synott and Buttler 12 and Lanier 13 ). Similarly, calorimetric data of aqueous {Na 2 SO 4 + NaCl} are very scarce; heats of mixing measurements of sodium sulfate and sodium chloride solutions were reported by Snra and Wood 14 at ambient temperature, and more recently, Conti et al 15 measured isobaric heat capacities for aqueous solutions containing the system Na-K-Cl-SO4 from 333 K to 473 K.…”