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.
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