A) Soda glass
B) Crooke's glass
C) Pyrax
D) None of these
Correct Answer: B
Solution :
The average composition of ordinary glass (soda glass) corresponds to the formula \[\text{N}{{\text{a}}_{\text{2}}}\text{O}\text{.CaO}\text{.6}\,\,\text{Si}{{\text{O}}_{\text{2}}}\text{.}\]Glass is a super cooled liquid. In the preparation of Crooke's glass a part of CaO is replaced by Pb, Ba or Mg. Cerium oxide \[\text{(Ce}{{\text{O}}_{2}}\text{)}\] is also added. This oxide cuts ultra violet radiations which are harmful for eyes and so is used in making special type of lenses (soda glass is the cheapest and the most common form of glass) Pyrex glass is made by fusing a mixture of sand, lime, borax \[(N{{a}_{2}}{{B}_{4}}{{O}_{7}}.10{{H}_{2}}O)\] and alkali carbonates. It has good chemical durability and thermal shock resistance. It is used for making laboratories apparatus, oven wares etc.
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