Thermodynamic analysis and correlation of solubility of disodium 5′-guanylate heptahydrate in aqueous ethanol mixtures

The solubility of disodium 5′-guanylate heptahydrate (5′-GMPNa2) in water-ethanol binary solvent mixtures was measured at temperatures ranging from 278.15 K to 323.15 K using a dynamic method. The solubility data were correlated by the Apelblat equation, the Combined Nearly Ideal Binary Solvent/Redlich–Kister (CNIBS/R–K) equation and the modified Jouyban–Acree equation, respectively. Results showed that a reasonable match with experimental data is obtained from the Apelblat equation and CNIBS/R–K equation, while the modified Jouyban–Acree equation contains parameters including both solvent composition and temperature. The thermodynamic functions Gibbs free energy, enthalpy and entropy of solution were also calculated based on solubility data of 5′-GMPNa2 determined in binary water + ethanol solvent mixtures by using van’t Hoff equation. The dissolving process is endothermic and the dissolution driving force converts from enthalpy-driving to entropy-driving.