D‐C, pulse, differential pulse, and linear sweep polarographic methods have been used to characterize the reduction as a function of water content in the eutectic melt at 145°C. For very small concentrations of water added to the anhydrous melt, anodic shifts were observed in the Ni(II) polarographic wave. This was accompanied by changes in the kinetic shape parameter, . At higher water concentrations cathodic shifts occurred in the half‐wave potentials and the waves became irreversible. These effects are attributed to dramatic changes in the coordination of the Ni(II) ion, especially the initial cleavage of the bidentate nitrate rings, rather than to adsorption of water molecules at the interface or catalytic acceleration of the reduction.