On fusion of a mixture of `Na-2CO_3` and ` CaCO_3` with silica at `1500^@C`, a liquid consisting of
Channel: Doubtnut
Date: 2020-07-26

On fusion of a mixture of `Na-2CO_3` and ` CaCO_3` with silica at `1500^@C`, a liquid consisting of silicatees of sdium and calcium is formed. On cooling . Liquid become viscous and eventually ceasesto flow . It becomes solid and is known as flass. By varying the proportions of the three basic ingredients and by adding other substances, the properties of glass can be altered, Glass can be represented as `R_2 O. MO.6SiO_2`, where `R= Na` or `K, M = CaBa, Zn` or `pbSiO_2` may be replaced by `Akl_2 O_3 , b_2 O_3` or `P_2 O_5`. Colourd glasses are obtained by adding certain metallic oxdes or salts in the fused mass, Glass is attached by `HF` and this property is used to make marking on the galss , This is known as etching . The glass on rapid coolling becomes brittle and fragile . The artciles of glass are cooled neither slowly nor very rapidly . The process of graducal cooling of flass iscalled annealing .   Glass is .