Partial molar volume of water in phonolitic glasses and liquids

The volumes and expansivities of four hydrous phonolite glasses and liquids have been measured by dilatometry from 300 K up to the glass transition an d over a 50 K interval just above the glass transition. The partial molar v olume of water is independent of the water content for the glass and liquid phases, with values of about 11.0 +/- 0.5 and 17.1 +/- 0.9 cm(3)/mol at 30 0 and 800 K, respectively. The partial molar thermal expansivity of water i n phonolite glasses is about 8x10(-5) K-1, a result similar to recently pub lished values for different silicate compositions, and about 36.5x10(-5) K- 1 in phonolite liquids. The implications for melt density and water dissolu tion are discussed.