Plaster of Paris

  • Calcium sulfate hemihydrate
  • Gypsum hemihydrate
Formula
2CaSO4 . H2O
Structure
Description
Fine, odorless, tasteless powder.

Registry Numbers and Inventories.
CAS
26499-65-0
RTECS
TP0700000
RTECS class
Other
Beilstein/Gmelin
8293 (G)
New Zealand
Listed

Properties.
Formula
2CaO4S . H2O
Formula mass
290.30
Melting point, °C
1297
Density
2.7 g/cm3 (20 C)
Solubility in water
Moderately soluble

Hazards and Protection.
Storage
Store in a cool, dry location. Keep containers tightly closed.
Handling
Product should be handled so as to reduce airborn dust generation.
Protection
Chemical splash goggles in compliance with OSHA regulations are advised; however, OSHA regulations also permit other type safety glasses. Whre chemical resistant gloves. To prevent repeated or prolonged skin contact, wear impervious clothing and boots.
Respirators
NIOSH approved dusk mask.
Small spills/leaks
Sweep up material and place in a container for disposal. Keep dust generation at a minimum. Wear protective equipment.
Stability
Stable at normal temperatures and pressures.
Incompatibilities
Strong oxidizing agents.
Decomposition
None known.

Fire.
Fire fighting
Wear a self-contained breathing apparatus in pressure-demand, MSHA/NIOSH (approved or equivalent), and full protective gear. During a fire, irritating and highly toxic gases may be generated by thermal decomposition or combustion. Use agent most appropriate to extinguish fire.

Health.
Exposure limit(s)
NIOSH REL: TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp) OSHA PEL: TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)
Exposure effects
Chronic bronchitis and respiratory tract leasions may result with high exposure levels.
   Inhalation
Irritation. High concentrations may cause impaired lung function.
   Skin
Irritation.
   Eyes
Irritation.

First aid
 
   Ingestion
Seek medical attention. If individual is drowsy or unconscious, do not give anything by mouth; place individual on the left side with the head down. Contact a physician, medical facility, or poison control center for advice about whether to induce vomiting. If possible, do not leave individual unattended.
   Inhalation
If symptoms develop, move individual away from exposure and into fresh air. If symptoms persist, seek medical attention. If breathing is difficult, administer oxygen. Keep person warm and quiet; seek immediate medical attention.
   Skin
Remove contaminated clothing. Wash exposed area with soap and water. If symptoms persist, seek medical attention. Launder clothing before reuse.
   Eyes
If symptoms develop, immediately move individual away from exposure and into fresh air. Flush eyes gently with water for at least 15 minutes while holding eyelids apart; seek immediate medical attention.

Transport.