The depolarization characteristics of nitrobenzene were studied using an amalgamated rotatin micro-disk cathode of copper in sulphuric acid medium. The cathode potential change with d was followed with and wrthout the addition of nitrobenzene under diierent conditions. With 30 % sulphuric acid, the plot of potential/log cd is linear and when nitrobenzene is added and held in suspension, the cathode potential is consrderably shifted to less negative values, indicating good depolarization at all cd%. However, when nitrobenzene is brought into homogenous solution by the addition of ethyl alcohol, good depolarization was observed only at low cd (40 A/CM; at high cd, the potential rapidly shrfted to the hydrogenevolution potitd.
When acid saturated with sodium sul hate is used, the potential/log cd plot has two distinct parts with different slopes. At cd > 2 A dm*), Na+ discharge occurs and the reaction appears to P be hydrogen evolution on a sodium-amalgam surface. With 10% and 5% sodium sulphate in the acid bath, inllexions occur in the potential/log cd curves at higher current densities.
Addition of nitrobenzene to these baths containing sodium sulphate gives good depolarization only at the lower cd range. Addition of ethyl alcohol is again found to lower the depolarization effect of nitrobenzene.
The effects are interpreted in terms of the zero-charge potential of the cathode.