LOW‐TEMPERATURE VISCOSITY OF ALKALI SILICATE GLASSES*

A bstract Using an improved technique, precision measurements of viscosities in the annealing range of temperature were made on sodium, potassium, and sodium‐potassium silicate glasses containing from 10 to 40 mol % alkali. The viscosities of certain of those glasses that contain both Na 2 O and K 2 O reach minima, and the temperature coefficients of viscosity, which are nearly equal for the Na 2 O and the K 2 O glasses, become considerably smaller. These conditions may explain the practical advantages of certain glasses containing both Na 2 O and K 2 O.