A ternary system composed of Ni/Cr2O3/MgO-Mixture was prepared by co-precipitation from the corresponding metal nitrates using Na2CO3at room temperature. The precipitant was thermally treated at 350 °C in nitrogen atmosphere, followed by reduction at 320 °C, and then stabilized against spontaneous oxidation in air by impregnating it in bidistilled water and allowing slow oxidation to lake place while water evaporates. The specific catalytic activity of the prepared Ni/Cr2O3/MgO mixture for the isotopic exchange of deuterium between hydrogen and water vapour was measured using an exchange apparatus. The specific surface area for the catalyst mixtures was evaluated by nitrogen adsorption al liquid nitrogen temperature and application of the BET-equalion. The specific metallic surface area, the degree of dispersion and the average particle size of Ni/Cr2O3/MgO catalyst mixtures were also calculated through chemisorption of pure hydrogen. Comparison of the specific catalytic activity with the surface characteristics of the mixed catalysts indicates that the catalyst of the highest activity for the deuterium exchange between hydrogen and water vapour exhibit maximum specific metallic surface area, maximum percentage dispersion and minimum particle size.