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 in situ electrochemical methods. The redox ratio was calculated from the currents measured by Repetitive Multi-Pulse Chronoamperometry. It appears that the redox ratio does not depend on the total copper concentration over the range 0.25 to 1 wt% Cu. However, the proportion of copper(II) was found to increase with increasing basicity, ie with increasing the sodium oxide content. We deduced from a model based on the formation of pure ionic oxocomplexes that the coordination number of the Cu(II) oxocomplex is greater than that of the Cu(I) oxocomplex. The difference between the coordination numbers, which is calculated from the experimental results is equal to 0.56. The fractional number is quite far from the integer that would indicate the occurrence of well defined oxocomplexes of copper.