A POTENTIAL PH DIAGRAM FOR SYSTEM CU-NH3-CL--H2O

The potential pH diagram for the system Cu-NH3-Cl--H2O has been calculated. Owing to the fact that there was a change of the NH3 and NH4+ activities with change in pH, the diagram provides for the existence of Cu-oxides both in alkaline and acidic regions, but their stability domains are interrupted by stability domains of ammonium complexes. In this respect they differ from the diagrams calculated by other authors for the system Cu-NH3-H2O. The possibility of the existence of ammonium complexes between the stability domain of Cu-oxides is very important for an elucidation of corrosion behaviour of brasses in aqueous solutions containing ammonia. In the acidic region the CuCl and CuCl2 respectively prove more stable than the copper ammonium complexes. © 1969 Pergamon Press.