A Study of Configuration Changes in Glass by Means of Density Measurements

JSGT 1948 V32 T309-T339

Changes of density with time in the transformation range have been studied in vitreous silica, a borosilicate glass and a soda–lime–silica glass. In previous papers attention has been drawn to the close analogy between the atomic structure of glasses and liquids, and the results of the present experiments are interpreted in the light of that analogy. As was expected this has necessitated consideration of the behaviour of more complex liquids. In the case of the borosilicate glass it was found that there are two processes, at least, causing volume changes. The slower one at a given temperature leads to an increase in volume as equilibrium from a higher temperature condition is approached, the other to a decrease. Possible interpretations of this behaviour are indicated in terms of the temperature variability of the miscibility of liquids and the behaviour of solutions in mixed electrolytes. In the case of fused silica the experiments suggest a negative coefficient of thermal expansion when equilibrium is attained. This is supported by other published work on vitreous silica and is now interpreted as indicating an increase of structural binding as the temperature decreases, that is, to the same underlying cause as the phenomenon of maximum density in water. No anomalies have been found yet in the case of soda–lime–silica glass, but in this case the time needed to reach equilibrium in the temperature range studied is so long that the work has not progressed very far.

R. W. Douglas & G. A. Jones