iodosobenzene wave was proportional to concentration up to 0.002 31 whether 4 X lO-30/0 methyl cellulose was present or not. Anodic wave heights in the region 0.001 t o 0.002 M were approximately equal to cathodic wave I for iodosobenzene when measured a t the same concentration. On this basis it appears likely that the anodic wave involves two electrons. Slope analysis (plot of E ' / ? VR. log I/Id -I) showed a linear relationship for the anodic wave and yielded a slope of 0.13 at either 0.001 or 0.002 M iodosobenzene. indicating an irreversible reaction between iodosobenzene and mercury. Iodosobenzene can be identified in the presence of iodoxybenzene by virtue of its different anodic behavior.