A Study of the Glasses Boric Oxide-Silica

JSGT_1928_V12_T169_T190

The presence of boric oxide in glasses is accompanied by very definite characteristics, which are indicated by the fact that the oxide has been employed widely in modern chemical and heat-resisting glasses because of the reduction which it brings about both in the corrosion suffered when such glasses are treated with water and in their thermal expansion. In a series of papers from this Department, however, it has been shown that this beneficial use of boric oxide has very strict limitations. In some series, indeed, notably when silica is progressively displaced in Kavalier's glass by boric oxide, there is no appreciable improvement in chemical durability; indeed, beyond a certain basic oxide content, the glass is rapidly broken down by water and chemical reagents; whilst there is no diminution in thermal expansion but rather (again beyond a certain limit) an increase in value. The simpler series of soda–boric oxide–silica glasses, obtained by the progressive substitution of silica by boric oxide, are associated with maxima or minima in the curves which correlate the composition and a particular physical property.

[Related paper JSGT_1925_T389-T405.pdf]

Arnold Cousen & W. E. S. Turner