Viscosity and density data were obtained for several series of alkali aluminosilicate melts between 1200deg; and 1700deg;C with a counterbalanced sphere viscometer. Property comparisons are presented as functions of the SiO2content, Na2O content, and constant Al/Na ratios at 1500deg; and 1700deg;C.The viscosity and expansion information support the formation of threehyphen;dimensional cristobalitelike liquids on the Al/Na=1.0 line with some of the aluminum (III) in the form of AlO6octahedra for Al/Na1.0 melts.The molar volume models that coincide with experiment for Al/Nale;1.0 melts involve AlO4tetrahedra andvmacr;Na2Ovalues that increase with increase of the Al2O3content. The model that best agrees with experiment for melts with Al/Na1.0 involves only some of the excess aluminum ions in octahedral coordination as well as a changingvmacr;Na2O. Melt molar volume dependencies on composition can resemble those observed for similar glasses, which suggests structural similarities. The present liquid structure picture differs somewhat from previous concepts of aluminahyphen;rich glass structures in this ternary system.
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