Electrochemistry of the nickel-cyanide system at mercury electrodes: Part IV. Studies on the oxidation of Ni 2(CN) 64− at mercury electrodes

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The mechanism of Ni 2(CN) 6 4− electro-oxidation at mercury electrodes is investigated using cyclic voltanunetric and chronocoulometric methods. Ni 2(CN) 6 4− (existing presumably in the form of various ion-pairs {Ni 2(CN) 6 4−, x Na +}) is surface-active and manifests itself by the formation of an anodic adsorption wave. In the absence of an excess of free ligand, surface-active nickel cyanide was formed as one of the products of Ni 2(CN) 6 4− electro-oxidation on mercury. It was found that one cyanide ion was consumed in the rate-determining step of the electrooxidation of each Ni 2(CN) 6 4− particle. Within the potential range of mercury oxidation to Hg(CN) p (2− p) + and in the presence of both CN − and Ni 2(CN) 6 4− ions, small latent limiting currents are caused by the reaction 2 Ni(I) + Hg(II) → 2 Ni(II) + Hg(0) The scheme proposed for the participation of CN − ions in Ni 2(CN) 6 4− electro-oxidation was confirmed by the results of digital simulation of an appropriate model system.