Layered ƒÁ-titanium phosphate (ƒÁ-TiP), Ti(HP04)2.2H20, is well known as the host material of intercalation compounds and the inorganic ion-exchanger of H+/metal ion system. It was found to have high ion-exchange selectivity for Rb+ and Cs+ among alkali metal ions. The ionexchange reactions for these ions progressed in two steps according to pH. Part of water molecules in the mterlayer of ƒÁ-TiP was taken away during ion-exchange reaction and an amorphous ƒÁ-TiP resulted. This phenomenon was first studied by thermal analysis and further investigation was carried out using solid NMR of 1 H and 133Cs in detail. Moreover, the interaction between Fe2+ and Cs+ for the ion-exchange reaction was investigated. Despite Fe2+ was hard to adsorb to ƒÁ-TiP, the amount of sorbed Fe2+ increased when Cs+ coexisted and the amount of sorbed Cs+ decreased.