Hydroxo complexes in alkaline solutions

Three further complexes have been reported to form in Ni(II) solutions above ca. pH = 9 Ni(OH)2(aq), Ni(OH)) and Ni(OH)4, based on the increasing solubility of Ni(OH)2(cr) in alkaline solutions. According to a re-evaluation, carried out in this review, only the hydrolysis constant of the second species (V.27) can be determined with reasonable certainty  

The values of these hydrolysis constants selected by [76BAE/MES] and [98PLY/ZHA], (see Appendix A) are based on a few experimental points of a single paper [49GAY/GAR]. These data can, however, be equally well described when only Ni(OH)j is assumed to be present. 

Three publications [49GAY/GAR], [80TRE/LEB2], [89ZIE/JON] report thermodynamic properties for the Ni(OH)2(aq) and Ni(OH), species. The hydrolysis constants for reactions (V.26) and (V.27) can be derived from solubility equilibria  

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