CHEMICAL AND ELECTROCHEMICAL-BEHAVIOR OF NICKEL IONS IN THE ZNCL2-2NACL MELT AT 450-DEGREES-C

The stability of nickel chloride and oxide as well as the electrochemi cal behaviour of the Ni2+ ion have been studied in ZnCl2-2NaCl melts a t 450-degrees-C by means of X-ray diffractions (XRD), potentiometry, c yclic voltammetry, chronoamperometry and chronopotentiometry. The stan dard potential of the redox couple Ni(II)/Ni(O) and solubility product of nickel oxide have been determined (E-degrees-Ni(s)/Ni(II) = - 1.00 6 +/- 0.001 V (against Cl2(1 atm)/Cl-), pKs = 4.8 +/- 0.1 in molality scale). These results have allowed the construction of E-pO2- equilibr ium diagrams. Nickel (II) reduction is close to the reversibility acco rding to the scheme: NiCl2(solvated) + 2e- --> Ni(s) + 2Cl-with a diff usion coefficient, D(Ni), close to 3 x 10(-6) cm2 s-1.