Plaster of Paris, ( CaSO4 . ½ H2O) Plaster of Paris is calcium sulphate hemihydrate, CaSO4 . ½ H2O . Preparation of Plaster of Paris It is prepared by heating gypsum to 393 K. 2 CaSO4 . 2 H2O ---------> 2 CaSO4 . ½ H2O + 3 H2O The following conditions are necessary: 1) The temperature should not be allowed to rise above 393 K because above this temperature, the … [Read more...] about Plaster of Paris