TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compound: The cation is protons, lithium ions, or sodium ions. The inorganic oxide cation exchange particles comprise at least one hydrated metal oxide. The hydrated metal oxide contains a metal such as molybdenum, tungsten, zirconium, titanium, ruthenium. The halogen is fluorine, and chlorine. The inorganic oxide cation exchange particles are characterized by open framework structures with channels for proton conduction above 200 degreesC and comprise at least one oxide superacid or oxides with highly hydrated surfaces. The oxide superacid is sulfated zirconia, sulfated alumina, sulfated titanium oxide, or sulfated titanium -aluminum oxide.    TECHNOLOGY FOCUS - POLYMERS - Preferred Matrix: The polymeric matrix comprises an oxidation resistant polymer material and is a synthetic organic polymer having melting point of 100, preferably 200, more preferably 300, degreesC and is fully or partially halogenated polymers. The polymeric matrix is non-conducting. The membrane has Gurley number greater than 10,000 seconds. The polymeric matrix is formed by a blend of two or more synthetic organic polymers having melting point greater than 100 degreesC.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Compound: The cation-conducting material contains an organic and inorganic ion exchange material. The organic ion exchange material is perfluorosulfonic acid, and perfluorocarboxylic acid. SPECIFIC COMPOUNDS - The inorganic oxide cation exchange particles are heteropolytungstates, heteropolymolybdates, complex polyanions of tantalum and niobium, zirconium phosphates, hafnium phosphates, lead phosphates, tin phosphates, antimonic oxoacids. The polymeric matrix is perfluorosulfonic acid, polytetrafluoroethylene, perfluoroalkoxy derivatives of polytetrafluoroethylene, polysulfone, polymethylmethacrylate, silicone rubber, sulfonated styrene-butadiene copolymers, polychlorotrifluoroethylene, perfluoroethylene-propylene copolymer, ethylene-chlorotrifluoroethylene copolymer, polyvinylidenefluoride, copolymers of polyvinylidene fluoride with hexafluoropropene and tetrafluoroethylene, copolymers of ethylene and tetrafluoroethylene, polyvinyl chloride.    EXAMPLE - A porous polytetrafluoroethylene (PTFE) filter was placed in a filtration funnel, a suspension of gelatinous zirconium phosphate produced by the rapid addition of a solution of Zr(NO3)4.5 H2O to 85% phosphoric acid was placed in the funnel, and a vacuum applied to the outlet of the funnel. Fluid moved through the pores in the filter, but the gelatinous zirconium phosphate was retained, rapidly filling the pores and bringing the filtration to a stop after about 10 minutes. At the point the vacuum was released, that portion of the original suspension which had not yet passed into the filter was decanted, and the filter transferred to a boiling flask containing 85% phosphoric acid. A condenser was placed on top of the flask and the flask heated until the acid reached reflux. The beating was continued for seven days to crystallize the gel into alpha-Zr(HPO4)2.H2O. After the flask cooled, the acid was decanted and the membrane was removed. Since the crystalline phosphate occupied less volume than the amorphous gel, there was now pore volume open in the membrane. To ensure the complete filling of the pores, the filtration step was repeated, followed by the reflux step. The resulting membrane was washed in deionized water to remove any free phosphoric acid. The composite membrane fabricated above may be submitted to a Gurley air flow test to determine its gas permeability properties. The Gurley air flow test measured the time in seconds for 100 ml of air to flow through a one square inch sample at 4.88 inches of water pressure. The sample was measured in a Gurley Densometer (ASTM 0276-58). The sample was placed between the clamp plates. The cylinder was then dropped gently. The automatic timer (or stopwatch) was used to record the time (seconds) required for a specific volume recited above to be displaced by the cylinder. This was the Gurley number.