The oxidation of ethylene in a static system using evaporated films as catalysts (without promoters), gave yields of ethylene oxide at 240 °C which were highest over pure silver, decreasing to zero over alloy films with >40% palladium. The faster rate of CO 2 formation decreased slowly before increasing again—sharply above 90% Pd Ag —to a substantial maximum over pure palladium. The alloy catalysts required reactivation by hydrogen between rate measurements to determine activation energies; pretreatment of silver films with oxygen, ethylene oxide, etc., confirmed the association of ethylene oxide with the deactivation of silver catalysts. The high activity of palladium compared with silver for the complete oxidation to CO 2 is correlated with a lower heat of oxygen chemisorption. Most of the reported decrease in adsorption heat occurs near pure palladium, which is reflected in the present catalytic properties. The activation energy for CO 2 formation increased from ∼14 to ∼30 kcal/mole between ∼40 and ∼60% Pd, compensated by an increase in frequency factor. The extent to which silver enrichment at the surface, and hydrogen solubility in the lattice, may superimpose on a pattern of activity related to the electronic structure of the bulk is discussed. The reported rate of hydrogen-oxygen combination also falls rapidly when silver is added to palladium so that hydrogen dissolution in the lattice (see Part I, preceding paper) competes with its desorption as water. An explanation for the decrease in ethylene oxide formation with increasing palladium content was sought in variations between the modes of oxygen chemisorption. This variation may arise from changes in bulk electronic properties or surface structure; unchanged reaction rates over a 19% Pd Ag film, prepared with the palladium-rich structure, suggest the former.