REVISED POURBAIX DIAGRAMS FOR COPPER AT 25-DEGREES-C TO 300-DEGREES-C

The Pourbaix diagrams (potential-pH diagrams) for copper at 25 to 300 degrees C have been revised. Extrapolation of thermochemical data to e levated temperatures has been performed with the revised model of Helg eson-Kirkham-Flowers, which also allows uncharged aqueous complexes, s uch as CuOH(aq) and Cu(OH)(2)(aq), to be handled. Calculated high temp erature thermodynamic data have been fitted against experimental data at elevated temperature. The hydrolysis of copper(I) and (II) is inclu ded with two and four hydroxide complexes, respectively. The Pourbaix diagrams show that the oxides (Cu2O(cr) and CuO(cr)) are stable at 25 to 200 degrees C at 10(-6) mol kg(-1) of dissolved species, and at 300 degrees C only CuO is stable. The oxides are stable at 25 degrees C a t 10(-8) mol kg(-1), but at 100 to 300 degrees C no solid compound is stable.