typical oxide films. Also, we do not have the problem of electronic conduction which can complicate the metal oxide film growth kinetics. Despite these differences between the formation of organic coatings and metal oxide layers the same kinetic treatment applies to both processes.The kinetics of reduction of NO by H, over a supported ruthenium catalyst were explored in integral and differential reactor tests at atmospheric pressure and 100 to 350 O C with reactant concentrations of 60-3200 ppm of NO and 0.15-2.5% H, . The reduction of nitric oxide is half order to hydrogen and zero or negative order to nitric oxide, indicating a surface reaction between dissociatively adsorbed hydrogen and strongly chemisorbed nitric oxide or a surface species derived from it. Selectivity for ammonia formation depends only weakly on nitric oxide concentration; it increases with temperature from 100 to 200 O C , reaching a maximum of about 50% and then declining at higher temperatures. The decline is caused by the reaction of nitric oxide with ammonia or ammonia precursors rather than by the decomposition of ammonia.