SOLUBILITY AND SOLUBILITY PRODUCT OF CRYSTALLINE NI(OH)(2)

The solubility of crystalline Ni(OH)(2) was studied in solutions of 0. 01M NaClO4 with pH ranging from 7 to near 14. Equilibrium was approach ed both from over- and undersaturation, and the equilibration times ex tended from 3 to 90 days. The solubility of Ni(OH)(2)(c) in the pH ran ge of approximately 7 to 11.3 was effectively modeled by including aqu eous Ni2+ and NiOH+ species. Values of the logarithm of the thermodyna mic equilibrium constants for the reactions [Ni(OH)2(c) Ni2+ + 2OH(-)] and [Ni2+ + OH- reversible arrow Ni(OH)(+)] were determined to be -16 .1 +/- 0.1 and 5.65 +/- 0.10, respectively. These data, in conjunction with Fitter ion interaction parameters given in the literature, were used to model the reported solubilities of Ni(OH)(2)(c) in chloride, s odium acetate, and potassium chloride solutions. The model predictions for these systems were in excellent agreement with the experimental d ata from the literature.