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What is gypsum ? |
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Answer» Plaster of paris Plaster of Paris, CaSO4.1/2 H2O or (CaSO4)2.H2OIt occurs in nature as gypsum and the anhydrous salt as anhydride. It is prepared by precipitating a solution of calcium chloride or nitrate with dilute sulphuric acid.On heating the monoclinic gypsum is first converted into orthorhombic form without loss of water. When the temperature reaches 120°C, the hemihydrates or plaster of Paris is the product. The latter losses water, becomes anhydrous above 200°C and finally above 400°C, it decomposes into calcium oxide. |
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