HIGH‐TEMPERATURE VISCOSITIES OF SODA‐SILICA GLASSES*

Abstract

A bstract A careful study of the viscosities of glasses composed of silica and between 22 and 40% soda shows that viscosity‐composition isotherms are smooth curves. The sharp minima at about 34% Na 2 O (and possibly at about 26% Na 2 O) observed by Preston 1 are found to be entirely absent. Neither time nor shearing stress has any effect upon observed viscosities in the region investigated as long as temperature constancy has been established. A study of deviations, i.e ., of individual points from the smooth isotherms, shows that these are all within the expected limits of experimental error.