Calcium Sulphate, CaSO4.1/2H2O
Calcium
Sulphate, CaSO4.1/2H2O
Calcium Sulphate or Plaster of Paris is hemihydrates of
calcium sulphate. It is obtained when gypsum, CaSO4.2H2O, is heatd to 393 K.
2(CaSO4.2H2O) → 2(CaSO4).H2O
+ 3H2O
Above 393 K. no water of crystallization is left and
anhydrous calcium sulphate, CaSO4 is formed. T his is known as ‘dead burnt
plaster.
It has a remarkable property of setting with water. On
mixing with an adequate quantity of water it forms a plastic mass that gets
into a hard solid in 5 to 15 minutes.
Uses
The largest use of plaster of Paris is in the building industry
as well as plasters. It is used for immoblising the affected part of organ
where there is a bone fracture or sprain. It is also employed in dentistry, in
ornamental work and for making casts of statues and busts.
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