Magnesium oxide
Magnesium oxide is a widely used ingredient in cosmetics, personal care, and skincare formulations. Depending on its function, it may serve as a moisturizer, preservative, emulsifier, or active ingredient to enhance the overall effectiveness and performance of a product.
Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to remove moisture.
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| Names | |
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| IUPAC name
Magnesium oxide
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Other names
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| Identifiers | |
3D model (JSmol)
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| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.013.793 |
| EC Number |
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| E number | E530 (acidity regulators, ...) |
| KEGG | |
PubChem CID
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| RTECS number |
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| MgO | |
| Molar mass | 40.304 g/mol |
| Appearance | White powder |
| Odor | Odorless |
| Density | 3.6 g/cm3 |
| Melting point | 2,852 °C (5,166 °F; 3,125 K) |
| Boiling point | 3,600 °C (6,510 °F; 3,870 K) |
| Solubility | Soluble in acid, ammonia insoluble in alcohol |
| Electrical resistivity | Dielectric |
| Band gap | 7.8 eV |
| −10.2·10−6 cm3/mol | |
| Thermal conductivity | 45–60 W·m−1·K−1 |
Refractive index (nD)
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1.7355 |
| 6.2 ± 0.6 D | |
| Structure | |
| Halite (cubic), cF8 | |
| Fm3m, No. 225 | |
a = 4.212Å
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| Octahedral (Mg2+); octahedral (O2−) | |
| Thermochemistry | |
Heat capacity (C)
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37.2 J/mol K |
Std molar
entropy (S⦵298) |
26.95 ± 0.15 J·mol−1·K−1 |
Std enthalpy of
formation (ΔfH⦵298) |
−601.6 ± 0.3 kJ·mol−1 |
Gibbs free energy (ΔfG⦵)
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-569.3 kJ/mol |
| Pharmacology | |
| A02AA02 (WHO) A06AD02 (WHO), A12CC10 (WHO) | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards
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Metal fume fever, Irritant |
| GHS labelling: | |
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| Warning | |
| H315, H319, H335 | |
| P261, P264, P271, P273, P280, P302+P352, P304+P340, P305+P351+P338, P312, P333+P313, P337+P313, P362, P363, P391, P403+P233, P405 | |
| NFPA 704 (fire diamond) | |
| Flash point | Non-flammable |
| NIOSH (US health exposure limits): | |
PEL (Permissible)
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TWA 15 mg/m3 (fume) |
REL (Recommended)
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None designated |
IDLH (Immediate danger)
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750 mg/m3 (fume) |
| Safety data sheet (SDS) | ICSC 0504 |
| Related compounds | |
Other anions
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Magnesium sulfide Magnesium selenide |
Other cations
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Beryllium oxide Calcium oxide Strontium oxide Barium oxide |
Related compounds
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Magnesium hydroxide Magnesium nitride |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Magnesium oxide was historically known as magnesia alba (literally, the white mineral from Magnesia), to differentiate it from magnesia nigra, a black mineral containing what is now known as manganese.
