Corrosion of silicate glasses by alkaline solutions Communication 2. Relation between the stability of glasses to alkali and their compositions

Abstract

1. The alkali -stabilities of glasses of the type (87 -−x)%SiO2, −x%RO, 13%Na2O (R is Be, Mg, Ca, Sr, Ba, Zn, Cd, or Pb), binary sodium silicate glasses containing 13–33 moles %Na2O, and titanium-containing flint glasses were determined by measuring the thickness of the dissolved layer interferometrically. 2. It was shown that, with the exception of beryllium oxide, all oxides introduced into the binary glass in place of silica lower the alkali-stability of the glass. At first (up to 22 % RO), the lowering is only slight and the glasses differ little in alkali-stability. When the amount of silica replaced by metal oxide is higher than this, there is a considerable fall in stability; this fall is the greater, the greater the ionic radius of the metal introduced (ionic-radius rule). 3. For sodium oxide contents of up to 20 moles percent, binary sodium silicate glasses are fairly stable. Titanium affects stability to alkali in the same way as lead.