Water and the density of silicate glasses |
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| Authors: | Pascal Richet Alan Whittington François Holtz Harald Behrens Susanne Ohlhorst Max Wilke |
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| Institution: | Laboratoire de Physique des Géomatériaux, Institut de Physique du Globe de Paris, ESA CNRS 7046, 4 place Jussieu, 75252 Paris cédex 05, France e-mail: richet@ipgp.jussieu.fr; Fax: +33-1-44272487, FR
Institut fur Mineralogie, Universit?t Hannover, 30167 Hannover, Germany, DE
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| Abstract: | A review of published and newly measured densities for 40 hydrous silicate glasses indicates that the room-temperature partial
molar volume of water is 12.0 ± 0.5 cm3/mol. This value holds for simple or mineral compositions as well as for complex natural glasses, from rhyolite to tephrite
compositions, prepared up to 10–20 kbar pressures and containing up to 7 wt% H2O. This volume does not vary either with the molar volume of the water-free silicate phase, with its degree of polymerization
or with water speciation. Over a wide range of compositions, this constant value implies that the volume change for the reaction
between hydroxyl ions and molecular water is zero and that, at least in glasses, speciation does not depend on pressure. Consistent
with data from Ochs and Lange (1997, 1999), systematics in volume expansion for SiO2–M2O systems (M=H, Li, Na, K) suggests that the partial molar thermal expansion coefficient of H2O is about 4 × 10−5 K−1 in silicate glasses.
Received: 30 June 1999 / Accepted: 5 November 1999 |
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