Calcium sulfate

 

Calcium sulfate

Chemical formula	CaSO4
OTP appearance	white solid
Molar Mass(g/mol)	136.14
Density(g/cc)	2.96
Melting Point(°C)	1460
Solubility in water(g/L)	2.1
NFPA 704	0 1 0

Uses

Primary

• The γ-anhydrite form (1-5 molar percent water) is the primary component of gypsum plaster

Natural occurrence

• -dihydrate occurs naturally as gypsum

Production

Extraction

from gypsum

• Heat gypsum to over 180°C producing anhydrite

Synthesis

as a byproduct

• During the production of phosphoric acid:

  Ca₃(PO₄)₂ + 3 H₂SO₄ → 2 H₃PO₄ + 3 CaSO₄

from chalk

• Combine sulfuric acid and calcium carbonate

  CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂

See Also

• Gypsum