Plaster of Paris, [CaSO4. H2O]Calcium sulphate with half a molecule of water per molecule of the salt (hemi-hydrate) is called plaster of paris (plaster of paris).
The temperature should be kept below 140°C otherwise further dehydration will take place and the setting property of the plaster will be partially reduced.
The first step is called the setting stage, and the second, the hardening stage. The setting of plaster of Paris is catalyzed by sodium chloride, while it is reduced by borax, or alum.Uses
- In surgery for setting broken or fractured bones
- For making casts for statues, in dentistry, for surgical instruments, and toys etc
- In making black board chalks, and statues
- In construction industry