SOLUBILITY AND THERMODYNAMICS OF SOLUBILITY OF CESIUM NITRATE IN MIXED 1,2-PROPANDIOL ‑ PROPAN-2-OL SOLVENT

N.V. Efimova, A.P. Krasnopyorova, E.N. Filippova 

Kharkov National University of V.N. Karazin, Svobody square 4, Kharkov, Ukraine
e-mail: alla.p.krasnopyorova@univer.kharkov.ua

Modern theories that explain the phenomenon of solubility of electrolytes and non-electrolytes take into account influence of a number of factors. An important role in the process of dissolution of substances has a nature of solvent. Considerable theoretical and experimental material about solubility of substances in water is presently accumulated. Far less works are devoted to solubility in non-aqueous and mixed solvents. 
In the presented work influence of composition of the mixed 1,2-propandiol ‑ propan-2-ol solvent and temperature on solubility of cesium nitrate was examined. 
Solubility of cesium nitrate was determined in interval of temperatures 293.15 – 323.15 K by method of isothermal satiation. The concentration of the saturated solution was determined by method of radio-active indicators using the isotope 133Cs. 
The analysis of received data showed that solubility changed in wide limits depending on composition of solvent and temperature. So solubility of CsNO3 at 298.15 K lower almost on two orders in propan-2-ol (1.910-4 mol/l) comparing with 
1,2-propandiole (5.710-2 mol/l). 
Dependence of logarithm of solubility on the reciprocal of dielectric conductivity of solvents has a linear kind. That's why it is possible to assume that a basic factor determining solubility of nitrate of cesium is a dielectric conductivity of solvents.
Temperature influences on solubility of cesium nitrate in the studied alcohols. Solubility of salt grows with the increase of temperature and dependence of logarithm of solubility submits equation
lg s= a + bt
Rely on information about dependence of solubility on temperature, thermodynamic descriptions of process of dissolution: free energy of Gibbs (∆G°s), entropy (∆Sºs) and enthalpy (∆H°s), are calculated. 
It is showed that the process of dissolution of CsNO3 in the studied system is conditioned by enthalpy. Comparison of values of ∆H°s for clean individual solvents shows that dissolution of CsNO3 in 1,2-propandiole thermodynamically more advantageous, than in propan-2-ol, while difference for Т∆Sºs in both solvents insignificantly. It stipulates the best solubility of cesium nitrate in 1,2-propandiole as compared to propan-2-ol.