Salts and minerals
Magnesium oxide vs magnesium hydroxide
Magnesium oxide (MgO, CAS 1309-48-4) and magnesium hydroxide (H2MgO2, CAS 1309-42-8) are both listed under respiratory, allergy and digestive drugs.
Magnesium oxide has a molar mass of 40.30 g/mol, magnesium hydroxide 58.32 g/mol.
Measured melting points are 2,825 °C for magnesium oxide and 350 °C for magnesium hydroxide.
On CompoundList, 448 suppliers list magnesium oxide and 263 suppliers list magnesium hydroxide.
Data last updated 7 October 2026
 |  | |
|---|---|---|
| Identity | ||
| Name in our database | Magnesium oxide | Magnesium hydroxide |
| CAS number | 1309-48-4 | 1309-42-8 |
| Molecular formula | MgO | H2MgO2 |
| Molar mass | 40.30 g/mol | 58.32 g/mol |
| IUPAC name | oxomagnesium | magnesium dihydroxide |
| EC number | 215-171-9 | 215-170-3 |
| Physical properties | ||
| Appearance | White, very fine powder | Amorphous powder |
| Melting point | 2,825 °C | 350 °C |
| Boiling point | 3,600 °C | Not recorded |
| Density | 3.6 g/cm³ | 2.36 g/mL |
| Solubility | In water, 86 mg/L at 30 °C | White, friable masses or bulky, white powder, at about 700 °C is converted to MgO, sol in about 3,300 parts CO2-free water, more sol in water containing CO2, sol in dilute acids with effervescence, insol in alcohol /Magnesium carbonate… |
| LogP (octanol/water)Computed from the structure | -0.5 | -0.73 |
| Safety (GHS) | ||
| Signal word | None | None |
| Pictograms | None | None |
| Hazard statements | No hazard statements recorded | No hazard statements recorded |
| Uses and classification | ||
| Uses and functions |
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| Category | Inorganic chemicals › Oxides and peroxides | Inorganic chemicals › Hydroxides and bases |
| HS code | 251990Natural magnesium carbonate (magnesite), fused magnesia, dead-burned (sintered)… | 281610Hydroxide and peroxide of magnesium |
| Market on CompoundList | ||
| Suppliers | 448 suppliers | 263 suppliers |
| Supplier countries | 60 countries, most in India, United States, China | 39 countries, most in United States, India, China |
| Price rangeOnly prices set by suppliers who manage their own profile | Price on request | Price on request |
Measured and computed values as shown on each chemical page, plus live listings on CompoundList. Details may have changed, please confirm them with the supplier. Safety data is a summary, not an SDS.
Magnesium oxide
Magnesium hydroxide
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