IN-SITU ELECTROCHEMICAL INVESTIGATION OF COPPER IN BINARY SODIUM-SILICATE MELTS AT 1000-DEGREES-C

The influence of the melt composition on the redox ratio of copper in binary sodium silicates at 1000 degrees C was determined by means of i n situ electrochemical methods. The redox ratio was calculated from th e currents measured by Repetitive Multi-Pulse Chronoamperometry. It ap pears that the redox ratio does not depend on the total copper concent ration over the range 0.25 to 1 wt% Cu. However, the proportion of cop per(II) was found to increase with increasing basicity, ie with increa sing the sodium oxide content. We deduced from a model based on the fo rmation of pure ionic oxocomplexes that the coordination number of the Cu(II) oxocomplex is greater than that of the Cu(I) oxocomplex. The d ifference between the coordination numbers, which is calculated from t he experimental results is equal to 0.56. The fractional number is qui te far from the integer that would indicate the occurrence of well def ined oxocomplexes of copper.