Copper reacts readily with aqueous ammonia in the presence of oxygen, as follows: . The kinetics of this reaction were investigated over a wide range of and concentrations, oxygen pressures, temperatures, and stirring velocities. The rate of dissolution was proportional to the surface area of the copper, and, at low oxygen pressures, was determined by the transport of dissolved oxygen to the surface. When the pressure of oxygen, above the solution, was increased, the chemical reaction at the surface became rate‐controlling. Two dissolution reactions were found to proceed simultaneously and with independent rates, which were first order with respect to the concentrations of and , respectively. Both were independent of the concentration of oxygen. Mechanisms have been proposed for these reactions, consistent with the observed reaction products and kinetic results.