Abstract γ-Zirconium phosphate, Zr(HPO 4) 2 · 2H 2O, is an inorganic ion-exchanger with layer structure. Ethylene oxide taken up in the interlayer spaces suffers ring scission upon the reaction with monohydrogen orthophosphate groups on the interlayer surfaces and forms an organic derivative of the layered phosphate having phosphoric ester bonds, Zr(HOC 2H 4OPO 3) 2 · H 2O. These phosphoric ester groups on the interlayer surfaces are exchanged with phosphate ions of external solutions. The exchange proceeds rapidly in NaH 2PO 4 solution and the phosphoric ester ions are released into the solution. The rate of exchange is first-order and the derivative changes into the Na ion half-exchanged phase of γ-zirconium phosphate which reverts to the initial hydrogen form of γ-zirconium phosphate by washing with hydrochloric acid. This series of reactions makes a cycle and γ-zirconium phosphate can be used repeatedly for the formation of phosphoric esters, which can be regarded as a catalyst in a sense that zirconium is not consumed in the cycle.