Overview

Calcium sulfate (KAL-see-um SUL-fate) occurs in three forms:

• anhydrous calcium sulfate (CaSO₄); the anhydrous form of calcium sulfate is available in two forms, known as insoluble anhydrite and soluble anhydrite;
• calcium sulfate dihydrate (CaSO₄·2H₂O), also known as mineral white, terra alba, light spar, precipitated calcium sulfate, native calcium sulfate, and by other names;
• calcium sulfate hemihydrate (CaSO₄·1/2H₂O), also known as plaster of Paris and dried gypsum;

Key Facts

Other Names:

Anhydrous gypsum; also see Overview for synonyms of hydrates

Formula:

CaSO₄

Elements:

Calcium, sulfur, oxygen

Compound Type:

Salt (inorganic)

State:

Solid

Molecular Weight:

136.14 g/mol

Melting Point:

1460°C (2660°F)

Boiling Point:

Not applicable

Solubility:

Insoluble in water and most organic solvents

The physical properties of the three forms of calcium sulfate differ somewhat from each other, but their chemical properties are essentially the same. Anhydrous calcium sulfate and calcium hemihydrate are...