The Ion - Solvent Interaction and Ionic Association in Solvent Mixtures. -The Conductance of Potassium Halides and the Behaviour of Ions in n-Propanol-Water and iso-Propanol-Water Mixtures at 25°C.-

摘要

The conductance of potassium halides in vicinity of azeotropic mixture of n-PrOH, iso-PrOH and water was measured at 25°C. The results were analyzed by using Fuoss-Onsager conductance equation, Walden's equation and discussed about the solvent structure.In both solvent mixtures, n-PrOH - water and iso-PrOH - water, the limiting equivalent conductance of KCl, KBr and KI decrease along with the concentration of PrOH (mol%), due to decreasing of the dielectric constant and increasing of the association constant. There is noticeable difference between the ion-solvent interactions of Cl^- and Br^- and that of I^- and the difference increases together with increasing of PrOH concentration. The Walden product decreases as the concentration of PrOH increase, by reason of the effect of ionic equivalent conductance. In both solvent mixtures, n-PrOH - water and iso-PrOH - water, the Stokes' radii of halide ions are numerically almost equal in the vicinity of PrOH - water mixtures with 19mol%PrOH. On the other hand, in the vicinity of PrOH - water mixtures with 49mol%PrOH, the Stokes' radius of I^- is smaller than those of Cl^- and Br^- which are almost equal. What more, in the iso-PrOH - water mixtures with 68.05mol%, almost same tendency as mentioned above is observed. It will be considered that such tendency is inferred from the big difference of B coefficient of viscosity of I^- from those of Br^- and Cl^-, that is, I^- ion is strong structure breaker, and then the apparent size of I^- ion will be small in the solvent mixture.The association constants of KCl, KBr and KI in the both solvent show the tendency to increase in accordance with decreasing of the dielectric constant. It could be anticipated by the use of the Bjerrum's and Fuoss' equation. However, it is hard to discuss about the difference of ion-solvent interactions of halide ions by use of the data obtained. It requires more detail data to analyze.The characteristic ion-solvent interaction in the vicinity of azeotropic mixtures of n-PrOH - water and iso-PrOH - water is not observed.