On heating gypsum at 373 K, it loses water molecules and becomes?

On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate

 (CaSO₄ .1/2 H₂O ). This is called Plaster of Paris, the substance which doctors use as plaster for supporting fractured bones in the right position. Plaster of Paris is a white powder and on mixing with water, it changes to gypsum once again giving a hard solid mass.