Thermodynamics of the solubility of barium nitrate in the mixed solvent, ethanol+water, and the related ion-association

Abstract: Using the evaporating method, the solubility of barium nitrate was determined in various mixtures containing water and ethanol at 25.0 °C. The results show that the solubility of Ba(NO3)2 decreases when increasing mass percent of ethanol in the mixtures. This trend is along with decreasing the dielectric constant of “water+ethanol” mixture. Moreover, it can be concluded that the total solubility of Ba(NO3)2 may be regarded as the sum of two contributions; one referring to the free ions in the solution and the other to the BaNO3 +–ion pair which is formed in the saturated solution. Estimating the formation constant, K A, for the reaction, Ba(soln) 2+ +NO3(soln) − ⇄BaNO3(ion-pair) + according to Bjerrum or Fuoss models, it is quite easy to evaluate the contributions of free ions and BaNO3 + (ion-pair) to total solubility. [Copyright &y& Elsevier]