1. Basic Properties

Physical Properties:

Appearance: White or off-white powder, odorless and tasteless.

Density: 3.58 g/cm³ (25℃).

Melting Point: 2852℃, Boiling Point: 3600℃, Excellent high-temperature resistance.

Solubility: Insoluble in water, slightly soluble in acids, easily soluble in ammonium salt solutions.

Chemical Properties:

Basic oxide, can react with acids to form magnesium salts and water (e.g.: MgO + 2HCl → MgCl₂ + H₂O).

At high temperatures, can react with carbon to form elemental magnesium (MgO + C → Mg + CO).

Hygroscopicity: When exposed to air, it slowly absorbs moisture and carbon dioxide, forming magnesium bicarbonate.

2. Preparation Methods

Calcination Method: High-temperature calcination of magnesium carbonate (MgCO₃) or magnesium hydroxide (Mg(OH)₂) to obtain.

 MgCO₃ → Δ MgO + CO₂↑ MgCO₃ Δ MgO + CO₂ ↑

Precipitation Method: Through the reaction of magnesium chloride with alkali (such as sodium hydroxide) to generate magnesium hydroxide, and then calcination to obtain magnesium oxide.

Other methods: Such as extracting magnesium from seawater/brine, directly oxidizing metallic magnesium, etc.

3. Classification (by purity and application)

Industrial-grade Magnesium Oxide: Low purity (90-95%), used in refractory materials, metallurgy, etc.

Food/Pharmaceutical-grade Magnesium Oxide: High purity (≥98%), used as an antacid, food additive.

High-purity Magnesium Oxide (99.9% or above): Used in high-tech fields such as electronics, optical materials.

4. Main Applications

Refractory Materials: Used as the inner lining of high-temperature equipment such as steel furnaces and cement kilns (due to high melting point).

Environmental Field: Treat acidic wastewater or exhaust gas (neutralize acidic substances).

Medicine and Food:

Antacid (relieve excessive stomach acid).

Food Additive (anti-caking agent, magnesium element supplement).

Agriculture: Improve acidic soil or use as magnesium fertilizer. Others:

Fillers for rubber and plastic.

Raw materials for preparing other magnesium compounds (such as magnesium sulfate).

High-purity magnesium oxide is used in semiconductors, ceramics, etc.

5. Safety Precautions

Inhalation risk: The powder may irritate the respiratory tract. Wearing a protective mask is necessary.

Contact with skin: Generally harmless, but high concentration may cause mild irritation.

Storage: Sealed and protected from moisture. Avoid contact with acidic substances.

6. Extended Knowledge

Nano-magnesium oxide: Has a larger specific surface area and activity, used in catalysis, antibacterial materials, etc.

Difference from magnesium hydroxide: MgO is an oxide, while Mg(OH)₂ is a hydroxide (the latter is more prone to react with acids).