Studies on ion-exchange resins. V. Water vapor sorption

1. 1. Water vapor sorption studies on a series of ion-exchange resins are presented. The systems investigated include sulfonic acid cation-exchange resins of various degrees of cross-linking, a carboxylic acid resin, and a quaternary ammonium anion-exchange resin. 2. 2. Some direct calorimetric measurements of heats of sorption are presented. Free energies, heats of sorption, and entropies are calculated. 3. 3. The sorption behavior of sulfonic acid resins is compared with that of sulfuric acid. It is concluded that the sulfonic acid groups are osmotically inactive. For the sulfonic acid resins, variations in sorption with ionic state are discussed and interpreted. The partial molal volumes of the hydrated resin systems are studied. 4. 4. The behavior of the cross-linked polystyrene sulfonic acid resins is discussed from the point of view of simple, strong electrolytes in aqueous media. This interpretation is valid for the range 0–75% relative humidity; the influence of cross-linking makes itself felt above this point.