After the addition of 3.846 mM free cyanide to PAX solution as shown in Fig. 11(b), the peaks corresponding to the formation of elemental sulphur and dixanthogen disappeared. Thus free cyanide inhibited all electrochemical reactions on freshly abraded pyrite. It was also revealed by Janetski et al. (1977) that the oxidation of xanthate shifted to more anodic position and the anodic curve for pyrite oxidation showed little change with the increase of free cyanide concentration. It seems that the cyanide concentration in the present study is sufficiently high, resulting in the merging of xanthate oxidation peak with the background current due to the anodic reactions of the mineral itself. In the presence of 3.846 mM cuprous cyanide, the anodic and cathodic reactions were also largely inhibited and peak A2 for the oxidation of xanthate disappeared as shown in Fig. 11(b). However, the anodic oxidation to elemental sulphur still occurred, but less noticeably compared to that in background solution.