There is some interest in the speciation of water in silicate glasses and melts, and the effect of bulk composition on this speciation. We have obtained infrared and Raman spectra for SiO2-H2O glas;ses with low (1200 ppm) and high (6.3 wt%) water contents. The low-water-content glass shows an asymmetric band in the fundamental O-H stretching region, consistent with an SiOH species involved in a range of hydrogen-bonding environments. The high-water-content sample shows features due to both hydroxyl groups, as observed for the low-water-content glass, and molecular H2O dissolved in the glass. This sample also shows a Raman band at 3598 cm-1, which probably corresponds to a new type of SiOH species. We have also obtained the Raman spectrum for a sodium silicate glass Na2O⋅ 4SiO2 containing 1 wt% H2O. Addition of water to this composition causes considerable changes in the silicate band region below 1200 cm-1. The O-H stretching bands are very different to those observed for the SiO2-H2O glasses, and a weak band near 2350 cm-1 may correspond to SiOH groups involved in intratetrahedral hydrogen bonding, across an edge of the SiO4 tetrahedron.

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