Physical Properties of Boric Oxide Containing Glasses and their Bearing on ......

JSGT 1923 V07 T155-T169

Attention has already been directed to the influence which the addition of boric oxide has on the rate of melting and working of glass, on its lampworking properties, its tendency to devitrification, and its general durability. Numerical data which would make possible a strict comparison of the variation of these properties with the composition were not given to any considerable extent, the effects discussed being considered rather qualitatively than quantitatively. In the case of the annealing temperature, however, it has already been shown by us in a further paper that the addition of boric oxide in two series of sodium-borosilicates led certainly in the one case, and most probably in the other, to a rise of annealing temperature to a maximum value, after which there was a decline. We now propose to describe the results of measurements on three other properties, namely, the thermal expansion, the density, and the refractive index (including the dispersion). We shall see that in all these cases there are noteworthy effects which, except in one isolated instance to be referred to later, have not previously been noted during the study of the relationship between the physical properties and the composition of glass.

S. English & W. E. S. Turner