Gypsum hemihydrate
(CaSO4)2•H2O
Molecular mass: 290.3
ICSC # 1217
CAS # 26499-65-0
RTECS # TP0700000
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Types of Hazard/ Exposure
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Acute Hazards/ Symptoms
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Prevention
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First Aid/
Fire Fighting
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FIRE
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Not combustible.
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In case of fire in the surroundings: use appropriate extinguishing media.
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Explosion
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Exposure
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•Inhalation
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Cough.
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Local exhaust or breathing protection.
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Fresh air, rest.
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•Skin
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Protective gloves.
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Rinse and then wash skin with water and soap.
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•Eyes
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Redness.
Pain.
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Safety spectacles.
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First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor.
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•Ingestion
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Do not eat, drink, or smoke during work.
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Rinse mouth.
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Spillage Disposal
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Storage
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Packaging & Labelling
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Sweep spilled substance into containers; if appropriate, moisten first to prevent dusting.
Personal protection: P1 filter respirator for inert particles.
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Dry.
Well closed.
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Important Data
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Physical State; Appearance:
FINE HYGROSCOPICWHITEPOWDER
Physical Dangers:
Chemical Dangers:
Occupational Exposure Limits:
TLV: (as total dust containing no asbestos and <1 % crystalline silica) 10 mg/m3 as TWA; (ACGIH 2004).
MAK: (as respirable fraction of the aerosol, without fibers) 6 mg/m3 (DFG 2004).
OSHA PEL: TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)
NIOSH REL: TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)
NIOSH IDLH: N.D. See: IDLH INDEX
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Routes of Exposure:
Inhalation Risk:
A nuisance-causing concentration of airborne particles can be reached quickly when dispersed, especially if powdered.
Effects of Short-Term Exposure:
May cause mechanical irritation.
Effects of Long-Term or Repeated Exposure:
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Physical
Properties
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Melting point: 163°C
Density: 2.76 g/cm3 for the alpha hemihydrate
Density: 2.63 g/cm3 for the beta hemihydrate
Solubility in water, g/100 ml at 25°C: 0.30
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Environmental
Data
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N O T E S
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Other CAS number is 10034-76-1.
The apparent melting point caused by loss of crystal water is given.
Melting point for the anhydrous form is 1450°C.
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ADDITIONAL INFORMATION
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ICSC: 1217
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PLASTER OF PARIS
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(C) IPCS, CEC, 1994
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IMPORTANT LEGAL NOTICE:
Neither NIOSH, the CEC or the IPCS nor any person acting on behalf of NIOSH,
the CEC or the IPCS is responsible for the use which might be made of this
information. This card contains the collective views of the IPCS Peer Review Committee and may
not reflect in all cases all the detailed requirements included in national legislation
on the subject. The user should verify compliance of the cards with the relevant legislation
in the country of use.
The only modifications made to produce the U.S. version is inclusion of the OSHA PELs, NIOSH RELs and NIOSH IDLH values.
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