Abstract: Glass compositions of the SiO.sub.2 -ZrO.sub.2 -alkali metal oxide-alkaline earth oxide system containing 70-82 mole percent SiO.sub.2 and 2-8 mole percent ZrO.sub.2 and alkali metal oxides and alkaline earth oxides, and optionally Al.sub.2 O.sub.3, in specified amounts, such glasses being resistant to water, acids and alkalies, having a low to medium thermal coefficient of expansion and a low liquidus temperature.

Abstract: Glass batch compositions for producing low to medium expansion glasses having linear coefficients of thermal expansion in the range of from about 4.1 .times. 10.sup.-.sup.7 to about 19.0 .times. 10.sup.-.sup.7 in./in./.degree.C. over a temperature range from 0.degree.-300.degree..C. The glass batch compositions are capable of being melted at a temperature of about 1600.degree.C. and are composed essentially of a finely divided admixture of 70-87 mole percent SiO.sub.2 and 1.0-10 mole percent AlPO.sub.4 together with 0-21 mole percent of at least one RO.sub.2 oxide selected from the group consisting of from 0-14 mole percent TiO.sub.2 and 0-10 mole percent GeO.sub.2. The total mole percent of SiO.sub.2 and AlPO.sub.4 preferably constitute at least 79 mole percent of the total glass batch composition.