WatersorptionisothermsavailableintheliteraturesofNa^+-fromofDowex50W×4and×8,BioRex-70,Amberlyst-15,Nafion-117,hydroustitaniumoxide,crystallinezirconiumphosphateandzinchexacyanoferrate(Ⅱ）,havebeenanalysedbytheD′ArcyandWattequation.HydrationofNa^+intheionexchangersisthepredominantinteractionofsorbedwater.Thecorrelationbetweenthehydrationnumbersandthoseobtainedforelectrolytesolutionisfoundinthispaper.Qualitativeimplicationsofthestateofsorbedwaterintheionexchangersonitsvariouscharacteristicquantitieslikeselectivity,arebrieflydiscussed.
