Kinetics of the oxidation of the hexacyanodinickelate(I) anion by water

Abstract

The oxidation of the hexacyanodinickelate(I) anion has been studied spectrophotometrically and obeys the rate law –da/dt=(k₁[CN^–]+k₂[HCN])a(i), in which a represents the concentration of the anion. The spectrum of the anion has been measured between 240 and 620 nm. and found to have maxima at 313 nm. (ε= 2·68 × 10⁴ cm^–1 l. mole^–1) and at 470 nm. (ε= 580 cm^–1 l. mole^–1). The results suggest that the oxidation rate is controlled by the disproportionation of the anion occuring in reactions (ii) and (iii). At 25° and an ionic strength of 1·1, k₁=(1·18 ± 0·02)× 10^–3 l. mole^–1 sec.^–1, Ni₂(CN)₆^4–+ CN^– [graphic omitted] Ni(CN)₃^3–+ Ni(CN)₄^2–(ii), Ni₂(CN)₆^4–+ HCN [graphic omitted] HNi(CN)₃^2–+ Ni(CN)₄^3–(iii) and k₂=(4·8 ± 0·2)× 10^–1 l. mole^–1 sec.^–1.