The values of the thermodynamic functions, DsolH, DsolG, and DsolS, of the gallic acid dissolution in different concentrations of ethanol–water solutions were calculated using equations (6), (8),and (9), respectively, and are reported in table 5.
The enthalpy of dissolution versus temperature, derived from experimental solubility data for each solution, is depicted in figure 3. Estimated enthalpies of dissolution from solubility measurements of gallic acid in each mixed solvent at different temperatures are comparable, with the major deviation corresponding to the less concentrated ethanol solution. For all the studied solutions,it was found that the enthalpy of dissolution is a linear function of temperature, thus giving a constant heat capacity of solution. When the solubility is at a maximum, the enthalpy of dissolution spent for the formation of solvent structure cavities is a minimum.