C

Calcium oxide

IUPAC: oxocalcium

CaO Inorganic Compounds CAS 1305-78-8
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Quick Reference
Formula / NotationCaO
CAS Number1305-78-8
Molecular Weight56.08
Melting Point4662 °F (NIOSH, 2024)
Boiling Point5162 °F at 760 mmHg (NIOSH, 2024)
Density3.3 at 68 °F (USCG, 1999) - Denser than water; will sink
SolubilityReacts with water (NIOSH, 2024)
AppearanceCalcium oxide appears as an odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in insecticides and fertilizers.
Also Known Asoxocalcium; Calcia; Calxyl; Gebrannter kalk; Unslaked lime; Calcium monoxide; Airlock; CALX; Calx usta; Chaux vive
CategoryInorganic Compounds

What is Calcium oxide?

Calcium oxide is a member of the class of calcium oxides of calcium and oxygen in a 1:1 ratio. It has a role as a fertilizer.

Formula & Notation

CaO

IUPAC Name: oxocalcium

Other Names / Synonyms: oxocalcium; Calcia; Calxyl; Gebrannter kalk; Unslaked lime; Calcium monoxide; Airlock; CALX; Calx usta; Chaux vive

Properties & Characteristics

Appearance: Calcium oxide appears as an odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in insecticides and fertilizers.. Molecular formula: CaO. Molecular weight: 56.08 g/mol. Boiling point: 5162 °F at 760 mmHg (NIOSH, 2024). Melting point: 4662 °F (NIOSH, 2024). Density: 3.3 at 68 °F (USCG, 1999) - Denser than water; will sink. Solubility: Reacts with water (NIOSH, 2024). Vapor pressure: 0 mmHg (approx) (NIOSH, 2024).

Physical Data

PropertyValue
Melting Point4662 °F (NIOSH, 2024)
Boiling Point5162 °F at 760 mmHg (NIOSH, 2024)
Density3.3 at 68 °F (USCG, 1999) - Denser than water; will sink
Molecular Weight56.08
SolubilityReacts with water (NIOSH, 2024)
AppearanceCalcium oxide appears as an odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in insecticides and fertilizers.

Uses & Applications

Used in industrial processes, materials science, semiconductor manufacture, ceramics, or as a catalyst.

Safety Information

May be corrosive, toxic, or an oxidising agent. Handle in well-ventilated area. Consult SDS before use.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Calcium oxide
Formula CaO
CAS Number 1305-78-8
Molecular Weight 56.08
Synonyms oxocalcium; Calcia; Calxyl; Gebrannter kalk; Unslaked lime; Calcium monoxide; Airlock; CALX; Calx usta; Chaux vive

Frequently Asked Questions

Calcium oxide is a member of the class of calcium oxides of calcium and oxygen in a 1:1 ratio. It has a role as a fertilizer.

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Editorial standards: Chemical data is sourced from peer-reviewed literature, CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA, and IAEA. For educational purposes only — always consult official SDS documentation and qualified professionals before handling chemicals.