Kinetic influences on studies of copper(II) hydrolysis by copper ion-selective electrode

The hydrolysis of micromolar solutions of copper(II) is dominated by the formation of a copper—hydroxy colloid, both in the presence and absence of atmospheric carbon dioxide. Presence of the colloid was inferred from the response of the copper ion-selective electrode and confirmed by light scattering measurements. The colloid is only slowly converted to thermodynamically more stable species, with the result that copper—carbonate complexes are not formed to any significant extent in solutions exposed to atmospheric carbon dioxide. However, copper—carbonate complexes are formed in solutions containing a constant amount of total carbonate. Speciation and complexation capacity measurements should be interpreted with caution because thermodynamic equilibrium may not be attained in solution.