ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 9, Number 2
JKCSEZ 9(2)
April 20, 1965 

Polarographic studies of reduction of Ni(Ⅱ)-CN complex on Hg-electrode have indicated that Ni(CN)42- is reduced by two paths, via one electron process Ni(CN)42- + e [1]↔[2] Ni(CN)43- =(eq) Ni(CN)2- + 2CN- and via two electron process Ni(CN)42- + 2e [3]→ 1/2[Ni(CN)33-]2 + CN- of which reduction [1] must be faster than reduction [3]. At very dilute cyanide concentration (0.004 to 0.01 M) cathodic wave is practically responsible for reaction [1] and two cyanide ions appear to contribute to the reaction. As increasing cyanide ion concentration the rate of oxidation reaction [2] catalysed by Hg increases and reaction [1] and [2] approach to equilibrium. Therefore, reaction [3] represents the cathodic wave at high concentration of cyanide (above 0.2 M). This mechanism can also explain the fact that limiting current at [CN-] = 8 M is approximately twice of that at 0.004 M CN.