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 and over a 50 K interval just above the glass transition. The partial molar volume of water is independent of the water content for the glass and liquid phases, with values of about 11.0ǂ.5 and 17.1ǂ.9 cm³/mol at 300 and 800 K, respectively. The partial molar thermal expansivity of water in phonolite glasses is about 8᎒^-5 K^-1, a result similar to recently published values for different silicate compositions, and about 36.5᎒^-5 K^-1 in phonolite liquids. The implications for melt density and water dissolution are discussed.