High temperature oxide melt solution calorimetric data have been obtained for glasses and crystals of sodium feldspar composition, NaAl (Si, Ge)3O8, with varying degrees of substitution of Ge for Si. A linear dependence on composition for the enthalpies of solution implies ideal mixing behavior for both crystalline and glassy phases. The results are discussed in light of the rather different reported viscosities for end-member melts. The thermodynamic data collected allow calculation of a simple phase diagram for this two-component system. The calculated value of KD=(XGec/XSic)/XGe1/XSi1) is 0.87±0.05.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.