... , physical properties: 1. Quartz glass consists mainly of silica (SiO2), content of 99.99%. Other impurity is infinitesimal, impurities total ... PPM. 2. Quartz glass resistance ability of nitrate than lead resistance ability of nitrate is 10000 times higher, resistance to ... glass softening temperature 1730 °C, using temperature 1200 °C. Coefficient of expansion: at normal temperature for 5 x 10-7 / °C ...