On heating gypsum it loses one and a half molecules of water and forms calcium sulphate hemihydrate also known as plaster of Paris.
CaSO4.2H2O → CaSO4.1/2H2O + 3/2H2O
Uses of Plaster of Paris
- Plaster of Paris is used by doctors for supporting fractured bones in the right position.
- It is used for making toys and decorative materials.
- It is also used for increasing smoothness of surfaces.