The investigation of ionic association in the CdF2 solution with the mixed solvent (water +ethanol +propanol) at 25°C

Using the mixed solvents, (water +ethanol + propanol), the solubility of CdF2 was determined by evaporating method at 25° C. The results showed that the sollbility, s, of CdF2 decreases by decreasing the dielectric constant of the mixed solvent .Once the solubility of CdF2 was determined, the concentration solubility product, Ksp(c)=4s3, was calculated .Furthermore ,by estimating the mean activity coefficient, f± , of CdF2 in the solution upon the extended Debye-Hückel theory, the model solubility Product constant of the salt, Ksp(m)=4s3 f± 3 was calculated .On the other hand we concluded the equilibrium constant of ion pair formation , KIP, on the basis of Fuoss contact ion pair model and we obtained the value of ion pair concentration in the mixed solvents, (water 85% +ethanol l5% + propanol 10%). The value of thermodynamic solubility product constant, Ksp(th), of CdF2 in the mixed solvent was evaluated at zero ionic strength upon the extrapolation method and the value of ion pair concentration was calculated in the considered solution and compared by fuoss model.