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54.1 GLASS

Glass is a transparent or translucent amorphous supercooled solid solution of silicates and borates. The most common silicates present are those of potassium, calcium and lead. It is not a true compound because its composition is not fixed. An approximate formula for ordinary glass may be given as


where R = Na or K and M = Ca, Ba, Zn or Pb

SiO2 component in the above general formula can be replaced by Al203, B2O3 or P2O5,

Some of the common physical characteristics types of glass are as follows:

  • Glass is generally transparent or sometimes translucent non-crystalline solid.
  • Glass does not have definite melting point. On heating, it gradually softens and can be moulded into any desired shape. It is this property which makes glass a useful material or making articles of different shapes and sizes
  • It is poor conductor of heat and electricity.
  • It has sufficiently high viscosity (>1013 poise).
  • Glass can incorporate colouring material preserving transparency.
  • Glass melts into a liquid at very high temperature.