Amorphous oxide and hydroxide phases

These equilibrium solids are denoted in the present review as Zr(OH)4 , though this is more a name than a real stoichiometric phase. For Reaction (V.17)  

The solubility of amorphous phases provide useful information for users of the database when modelling the behaviour of complex systems. Therefore this solubility product is included in the table of selected thermodynamic quantities even if stricto sensu it is not a well defined thermodynamic quantity. 

The Gibbs energy of formation can be calculated from this value  

A much higher value of G° (Zr(OH)4, am, fresh, 298.15 K) = - 1439.8 kJ-mof was proposed by [92SLO/KR1] based on a value for Af/7° within the limits of the uncertainty of the value proposed in the present review, but a much lower entropy estimate. A A,.77° value can be calculated from the careful measurements by Turnbull [61TUR2] for the heat of reaction of  

These values are not selected by this review since they do not refer to a crystalline phase. However, they are consistent with the choice made for iog, , (v.i7). 

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