The influence of the thickness of a Pd-Ru alloy membrane on the H-2 flux from binary mixtures containing about 5 and 20% CO, CO2, CH4, and steam has been studied. It has been shown that with a decrease in the membrane thickness from 30 to 10 mu m, the negative influence of these impurities on the H-2 flux increases. In experiments with pure H-2, it has been established that a decrease in the membrane thickness does not affect the nature of the rate-limiting step in the H-2 flow mechanism. The values for the effective activation energy of the H-2 permeability of the 30- and 10-mu m membranes are 13.6 and 23.4 kJ/mol, respectively. A mathematical model describing the flow of hydrogen from binary mixtures through membranes of various thicknesses with varying temperature and pressure is proposed.