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The results of high temperature solubility studies st ORNL are pizsented in which mainly direct pH measurements were made of aqueous solutions in contact with the crystalline solid phases: A1(0&, AIOOH, Fej04, Mg(UI-I)2, Nd(OH)s, and ZnO. Examples are highlighed of specific phenomena such as: the kinetics of gibbsite and boehmite dissolution and precipitation; the sppeamce ofmetastable equiliiria in the dissolution of Fe8O4; the extremely rapid precipitation of cr)JstalIine brucite, Mg(OH)2; and anomalies in the apparent solubility profiles nf AIO(OH) nad ZnO. General trends associated with the effects of temperature and ionic strength are mentioned. Some of the potentionietnc investigations were augmented by conventional batch {AIOIOH) md ZnO), and flow-through column {ZnO) experiments. In the addidonnal'case of ZnCr204, the exkemely low solubility of this spinel permitted application of ouly the latter technique and these results are discussed iU teims of the measured chromium levels that resulted from incongruent dissolution.

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