Calcium sulfate
Calcium sulfate hemihydrate | |
| Names | |
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| IUPAC name
Calcium sulfate | |
| Other names | |
| Identifiers | |
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3D model (JSmol) |
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| ChEBI |
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| ChEMBL | |
| ChemSpider | |
| DrugBank | |
| ECHA InfoCard | 100.029.000 |
| EC Number |
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| E number | E516 (acidity regulators, ...) |
| 7487 | |
| KEGG | |
PubChem CID |
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| RTECS number |
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CompTox Dashboard (EPA) |
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| Properties | |
| 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) |
| 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) |
| −49.7·10−6 cm3/mol | |
| 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) | |
| 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).
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 and cause permanent hardness when dissolved therein.