Calcium sulfate

Calcium sulfate
Names
	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	136.14 g/mol (anhydrous); 145.15 g/mol (hemihydrate) ; 172.172 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	0.26 g/100ml at 25 °C (dihydrate)
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 the inorganic compound with the formula CaSO₄ and related hydrates. In the form of γ-anhydrite (the anhydrous form), it is used as a desiccant. One particular hydrate is better known as plaster of Paris, and another occurs naturally as the mineral gypsum. It has many uses in industry. All forms are white solids that are poorly soluble in water. Calcium sulfate causes permanent hardness in water.

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