Calcium sulfate

Calcium sulfate
	Calcium sulfate hemihydrate
Names
	IUPAC name Calcium sulfate
	Other names Sulfate of lime; Plaster of Paris; Drierite; Gypsum
Identifiers
CAS Number	7778-18-9 ; (hemihydrate): 10034-76-1 ; (dihydrate): 10101-41-4 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:31346 ; (dihydrate): CHEBI:32583;
ChEMBL	ChEMBL2106140;
ChemSpider	22905 ;
DrugBank	DB15533;
ECHA InfoCard	100.029.000
EC Number	231-900-3;
E number	E516 (acidity regulators, ...)
Gmelin Reference	7487
KEGG	C13194 ; D09201;
PubChem CID	(dihydrate): 24928;
RTECS number	WS6920000; (dihydrate): MG2360000;
UNII	E934B3V59H ; (hemihydrate): 3RW091J48V ; (dihydrate): 4846Q921YM ;
CompTox Dashboard (EPA)	DTXSID9029699 ;
	InChI InChI=1S/Ca.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Key: OSGAYBCDTDRGGQ-UHFFFAOYSA-L ; InChI=1/Ca.H2O4S/c;1-5(2,3)4/h;(H2,1,2,3,4)/q+2;/p-2 Key: OSGAYBCDTDRGGQ-NUQVWONBAU;
	SMILES [Ca+2].[O-]S([O-])(=O)=O;
Properties
Chemical formula	CaSO4
Molar mass	136.141 g/mol (anhydrous); 145.149 g/mol (hemihydrate) ; 172.171 g/mol (dihydrate)
Appearance	white solid
Odor	odorless
Density	2.96 g/cm3 (anhydrous) ; 2.32 g/cm3 (dihydrate)
Melting point	1,460 °C (2,660 °F; 1,730 K) (anhydrous)
Solubility in water	dihydrate ; 2.63 g/L (25 °C)
Solubility product (Ksp)	4.93 × 10−5 mol2L−2 (anhydrous); 3.14 × 10−5 (dihydrate);
Solubility in glycerol	slightly soluble (dihydrate)
Acidity (pKa)	10.4 (anhydrous) ; 7.3 (dihydrate)
Magnetic susceptibility (χ)	−49.7·10−6 cm3/mol
Structure
Crystal structure	orthorhombic
Thermochemistry
Std molar; entropy (S⦵298)	107 J·mol−1·K−1
Std enthalpy of; formation (ΔfH⦵298)	−1433 kJ/mol
Hazards
NFPA 704 (fire diamond)	1 0 0
Flash point	Non-flammable
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp) [for anhydrous form only]
REL (Recommended)	TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp) [anhydrous only]
IDLH (Immediate danger)	N.D.
Safety data sheet (SDS)	ICSC 1589
Related compounds
Other cations	Magnesium sulfate; Strontium sulfate; Barium sulfate
Related desiccants	Calcium chloride; Magnesium sulfate
Related compounds	Plaster of Paris; Gypsum
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Calcium sulfate (or calcium sulphate) is an inorganic salt with the chemical formula CaSO
₄. It occurs in several hydrated forms; the anhydrous state (known as anhydrite) is a white crystalline solid often found in evaporite deposits. Its dihydrate form is the mineral gypsum, which may be dehydrated to produce bassanite, the hemihydrate state. Gypsum occurs in nature as crystals (selenite) or fibrous masses (satin spar), typically colorless to white, though impurities can impart other hues. All forms of calcium sulfate are sparingly soluble in water^[5] and cause permanent hardness when dissolved therein.

^ Lebedev, A. L.; Kosorukov, V. L. (2017). "Gypsum Solubility in Water at 25°C" (PDF). Geochemistry International. 55 (2): 171–177. Bibcode:2017GeocI..55..205L. doi:10.1134/S0016702917010062. S2CID 132916752.
^ D.R. Linde (ed.) "CRC Handbook of Chemistry and Physics", 83rd Edition, CRC Press, 2002
^ ^a ^b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 978-0-618-94690-7.
^ ^a ^b ^c NIOSH Pocket Guide to Chemical Hazards. "#0095". National Institute for Occupational Safety and Health (NIOSH).
^ Franz Wirsching "Calcium Sulfate" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH, Weinheim. doi:10.1002/14356007.a04_555

[1] Lebedev, A. L.; Kosorukov, V. L. (2017). "Gypsum Solubility in Water at 25°C" (PDF). Geochemistry International. 55 (2): 171–177. Bibcode:2017GeocI..55..205L. doi:10.1134/S0016702917010062. S2CID 132916752.

[2] D.R. Linde (ed.) "CRC Handbook of Chemistry and Physics", 83rd Edition, CRC Press, 2002

[b1-3] Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 978-0-618-94690-7.

[PGCH-4] NIOSH Pocket Guide to Chemical Hazards. "#0095". National Institute for Occupational Safety and Health (NIOSH).

[Ullmanns-5] Franz Wirsching "Calcium Sulfate" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 Wiley-VCH, Weinheim. doi:10.1002/14356007.a04_555

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