The mixed-alkali effect on the resistance of glass to water

Based on the composition of float glass, the resistance of glass to water, in which a small amount of K-2 O (0-1.0 wt%) was substituted for equivalent amount of Na-2 O, was investigated by means of glass grains testing. The components extracted from, the glass and total alkalinities in extraction solution were determined by atomic absorption spectroscopy and neutralizing method, respectively. The composition of the glass was 14.4 K-2 O + Na-2 O, 4.0 MgO, 8.2CaO, 1.4Al(2) O-3, 72.0 SiO2, and the minimum extraction ratio of oxides (maximum durability) occurred at a K-2 O/Na-2 O ratio of 0.051 (by weight) due to the presence of the mixed, alkali effect. The relative extraction ratio of alkali oxides (R-2 O) was greater than that of alkaline earth oxides (RO). By means of mixed, alkali effect and lowing relative contents of R-2 O in the glass, the resistance of float glass to water was improved and its mildew-proof ability was therefore increased.