To the question of variscite and metavariscite formation. Phase equilibria in the system Al2O3¬–H2O–P2O5
Sergeeva A. V.
Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2016. V. 145. N 6. P. 101-113
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Language: Russian
Abstract
Phase equilibria were analyzed in the quasi-triple system Al2O3—H2O—P2O5 in the field of co-existence of the aluminum hydrate phosphates with water solutions within interval of temperatures 25—90 °C. There was determined the boundary between stability fields of the high- and low-temperature polymorphous modifications of the AlPO4(H2O)2 compoud (metavariscite and variscite, respectively); temperature of their co-existence is around 63 °C. The state of coordinated water was considered according to vibration spectroscopy data, and there were distinguished states of strong bonding of water molecules (frequencies 3100 and 3366 cm–1) and states closed to the ice-Ih (3236 and 3449 cm–1).
Key words: variscite, metavariscite, polymorphism, phase equilibria, hydrates of salts, hydrogen bond.
