COLORADO STATE UNIV FORT COLLINS DEPT OF CHEMISTRY
Absorption spectra have been recorded for Nicl2 dissolved in 0.81 and 1.51 molar ratio AlCl31-butylpyridinium chloride as a solvent at room temperature. In basic chloride-rich melts, the NiII is present as NiCl42- with molar extinction coefficients a658 169 and A705 175 lmolcm. The reduction of the NiII ion species at vitreous carbon electrodes exhibited irreversible behavior in acidic melts but no NiCl42- ion reduction was detected in the basic solvent. Potentiometry gave a theoretical 2-electron Nernst slope for NiII additions in the acidic region and a fourth power Cl- ion dependence consistent with NiCl42- formation in the basic region. At 40 deg C, the NiNiII standard electrode potential on the mole fraction scale was determined to be 0.8000 or - 0.005 V vs. 21 Al reference, and an equilibrium constant for the dissociation reaction, NiCl42- in equilibrium with Ni2 4 Cl- was determined to be 1.2 or - 1.0 x 10 to the -46th power.