Electrochemical and spectroscopic analyses (UV-vis and XRD) have been applied to evaluate the speciation of copper in ammonia-chloride solutions. The conditions for these analyses were established through thermodynamic studies that included predominance existence and Eh-pH diagrams. These studies highlighted the importance of copper ternary complexes and showed how the solubility of Cu(I) and Cu(II) increases over a wide range of pH when copper ternary complexes are formed. Hence, it has been elucidated the copper, ammonia and chloride concentrations that makes existence of these so-called copper ternary complexes, possible. (c) 2007 Elsevier Ltd. All rights reserved.