Enthalpies of dilution of aqueous ionene solutions

Ile enthalpies of dilution (DeltaH(D), c --> 0.002 mol/dm(-3)) of aqueous s olutions of 3,3- 4,5- 6,6- and 6,9- ionenes with Br and Cl- counterions, re spectively, have been measured over a broad concentration range at 25 degre esC. The enthalpies of dilution show rather big dependence on the kind of t he counteriion, as well as large dependence on the charge density of ionene s. For 3,3- and 4,5- types dilution effects are endothermic, while for 6,6- and 6,9-ionenes are exothermic in the low concentration range and become e ndothermic in more concentrated solutions. The concentration dependence of the enthalpy of dilution of ionene solutions were compared with predictions of electrostatic cell theory. An agreement between theory and experiment w as found only if the effects of specific interactions were included in the calculations.