ABSTRACT
Most investigations concerned with the insoluble acid salts of tetravalent metals have been carried out on α-zirconium monohydrogen phosphate and its salt forms. The acid salts of tetravalent metals will be subdivided according to their crystalline structure as: acid salts with layered structure of α-type, acid salts with layered structure of γ-type, acid salts with fibrous structure, acid salts with three-dimensional structure, and acid salts having an as yet unknown structure. The differences between the ion exchange properties of α-layered exchangers seem to arise essentially from different dimensions of the unit cell. The pH value at which the exchange occurs must increase as the dimensions of the openings connecting the cavities decrease. The first fibrous acid salt of a tetravalent metal to be prepared was cerium (IV) phosphate. Fibrous acid salts are very interesting from a practical point of view because they can be employed to prepare inorganic ion exchange papers, or thin layers, suitable for fast separations of cations.
