Table 1.

Standard electrode potential (E°) of elements with an unstable +3-oxidation state. Value for Ni ref. [48]; all others values from [49].

Element	Standard Electrode Potential E° (V)
Ni(OH)3/Ni(OH)2	+1.31
Cu3+/Cu2+	+2.40
Co3+(aq)/Co2+(aq)	+1.92
Mn3+/Mn2+	+1.54
Fe3+(aq)/Fe2+(aq)	+0.77
Cr(VI)/Cr(III)	+1.36
Cr(III)/Cr(II)	−0.41