Titanium stability constant

There have only been a few studies that have examined the hydrolytic reactions of titanium(IV), with many obtaining unreliable solubility or stability constant data. Data for the monomeric species TiOOH to TiO(OH)g are available, with the neutral complex having a large pH region of stability. Although polymeric species have been postulated in a number of studies, the stoichiometry of the species is widely different in each of the studies and, as such, none of the data for these species are retained. 

Beukenkamp and Herrington (1960) and Nabivanets (1962) demonstrated that the distribution of titanium(lV) varies in proportion to the square of acidity, indicating that the charge on the titanium(lV) ion is +2, that is, the ion exists as TiO. This finding is consistent with studies that have used other techniques including solubility. However, the stability constants determined in these two studies lead to a stability that appears to be orders of magnitude too large and, as such, these data are not retained. 

Turiyan and Maluka (1982) obtained a stability constant for TiOH " " in l.Omoll" NaClO and at 25°C. The value they obtained was log j = —2.14. This value indicates a stability for TiOH greater than suggested by the other studies discussed earlier. At the titanium concentration studied, other studies suggest that the polymeric species Ti2(OH)2 should form. The absence of this species in the model postulated by Turiyan and Maluka may explain the enhanced stability of TiOH found by these authors. Thus, the data given in this study are not accepted by this review. Bakac, Marcec and Orhanovic (1977) obtained a stability constant for TiOH of log /ij = -2.42 0.03 in 1.0 mol 1 NaCl at 25°C which is very close to that obtained by Pocsi and Fabian (1988). This value is retained. 

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