Volumetric properties of the ternary system (CsCl + Cs2SO4 + H2O) and its subsystems from 283.15 to 363.15 K and atmospheric pressure: Experimental and thermodynamic model

The salt-water interactions on single salt aqueous solutions of cesium sulfate and cesium chloride, as well as their mixing solutions, have been investigated by a combination of density measurements by an Anton Paar Digital vibrating-tube densimeter and the correction of the Pitzer model of electrolyte. The volumetric properties including apparent molar volume ( V ϕ ) and the coefficient of thermal expansion of the solution ( α ) of the binary systems (CsCl + H 2 O), (Cs 2 SO 4  + H 2 O) and the ternary system (CsCl +  Cs 2 SO 4  + H 2 O) from 283.15 to 363.15 K at 5 K intervals and atmospheric pressure were derived. Variation trends of these volumetric properties against temperature and molality were revealed minutely. The Pitzer single salt parameters ( β MX 0 v , β MX 1 v and C MX v , MX = CsCl and Cs 2 SO 4 ), mixing ion-interaction parameters ( θ Cl , S O 4 v and ψ Cs , Cl , S O 4 v ) as well as the correlation coefficient a i in the temperature-dependence equation ( F ( i, p, j ) =  a 1  +  a 2 ln( T /298.15) +  a 3 ( T -298.15) +  a 4 /(620- T ) +  a 5 /( T -227)) have been obtained according to Pitzer ion-interaction model of electrolytes. These results are helpful to understanding the ion-interaction of aqueous solutions.