The Oxidation of Ammonia Solutions by Silver(II) Oxide

Abstract

The oxidation by silver(II) oxide of ammonia solutions varying in concentration from 0.09 to 0.97N has been studied in the temperature range 20-50°. The products of the oxidation were found to be nitrogen, ammonium nitrite, and ammonium nitrate. The amount of each product formed was found to be dependent on the concentration of ammonia present and the weight of silver oxide added, but independent of temperature. Rate equations for each product have been obtained in the form dA/dt = k(AgO)^x.(NH4OH)^y, where x is of the order of 1.6 and y has values of the order of 0.30 and zero for the formation of nitrogen and nitrate, respectively. For nitrite formation k equals zero. The constant k incorporates two constants, one of which is common to the three equations and is related to the formation of a transition complex on the surface of the solid. It is suggested that this initial step is a chemisorption process with an activation energy of about 18 kcal. A mechanism for the reaction and the role of silver oxide in oxidations of ammonia catalysed by silver salts are discussed.