Numerous experiments were carried out at relatively low pressures. The catalyst was a strip of platinum which was electrically heated. The walls of the reaction vessel were cooled down to liquid air temperature so as to condense certain of the products formed during the oxidation of ammonia. It is shown, experimentally and theoretically, that the intermediate products of reaction are hydroxylamine, NH3O, and nitrous acid, and that the mechanism of the combustion of ammonia may be expressed by the following series of reactions: