A thin layer of silica will be deposited on Vycor glass by CVD using the oxidation reaction of silane. The CVD reaction is highly pore-diffusion limited, so the deposition only occurs at the pore mouths. The depth of deposition can be controlled by adjusting the temperature and pressure. From the literature data on the rate of this reaction, a film of approximately 1 micron can be deposited at 300 C at 0.5-5 Torr pressure. The diffusivities of hydrogen and other gases through the composite membrane will be measured. Further, several equilibrium-limited reactions, in which hydrogen is a product, will be carried out in a tube formed by the composite membrane, in order to test the feasibility of the idea of reactor/separator. Success of the experiments could lead to the production of high temperature gas separation membranes and the possibility of a combined reactor-separator.