M

Magnesium hydroxide

IUPAC: magnesium dihydroxide

Mg(OH)2 Bases & Alkalis CAS 1309-42-8
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Quick Reference
Formula / NotationMg(OH)2
CAS Number1309-42-8
Molecular Weight58.320
Melting Point350 °C (decomposes)
Density2.36 g/mL
SolubilityPractically insoluble in water and in ethanol
AppearanceDry Powder, Liquid; Pellets or Large Crystals; Liquid; Water or Solvent Wet Solid; Dry Powder; Other Solid
Also Known Asmagnesium dihydroxide; 1309-42-8; Milk of magnesia; Magnesium dihydroxide; Magnesium hydrate; Magnesium hydroxide (Mg(OH)2); Magnesium(II) hydroxide; Phillips magnesia tablets; Magnesium (as hydroxide); Magnesii hydroxidum
CategoryBases & Alkalis

What is Magnesium hydroxide?

Magnesium dihydroxide is a magnesium hydroxide in which the magnesium atom is bound to two hydroxide groups. It has a role as an antacid and a flame retardant.

Formula & Notation

Mg(OH)2

IUPAC Name: magnesium dihydroxide

Other Names / Synonyms: magnesium dihydroxide; 1309-42-8; Milk of magnesia; Magnesium dihydroxide; Magnesium hydrate; Magnesium hydroxide (Mg(OH)2); Magnesium(II) hydroxide; Phillips magnesia tablets; Magnesium (as hydroxide); Magnesii hydroxidum

Properties & Characteristics

Appearance: Dry Powder, Liquid; Pellets or Large Crystals; Liquid; Water or Solvent Wet Solid; Dry Powder; Other Solid. Molecular formula: H2MgO2. Molecular weight: 58.320 g/mol. Melting point: 350 °C (decomposes). Density: 2.36 g/mL. Solubility: Practically insoluble in water and in ethanol.

Physical Data

PropertyValue
Melting Point350 °C (decomposes)
Density2.36 g/mL
Molecular Weight58.320
SolubilityPractically insoluble in water and in ethanol
AppearanceDry Powder, Liquid; Pellets or Large Crystals; Liquid; Water or Solvent Wet Solid; Dry Powder; Other Solid

Uses & Applications

Used in chemical manufacturing, pH adjustment, saponification, water treatment, and as a laboratory reagent.

Safety Information

Corrosive or irritant. Causes burns to skin and eyes. Store away from acids. Wear protective gloves and goggles. Consult SDS before use.

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

Key Facts

Term Magnesium hydroxide
Formula Mg(OH)2
CAS Number 1309-42-8
Molecular Weight 58.320
Category Bases & Alkalis
Synonyms magnesium dihydroxide; 1309-42-8; Milk of magnesia; Magnesium dihydroxide; Magnesium hydrate; Magnesium hydroxide (Mg(OH)2); Magnesium(II) hydroxide; Phillips magnesia tablets; Magnesium (as hydroxide); Magnesii hydroxidum

Frequently Asked Questions

Magnesium dihydroxide is a magnesium hydroxide in which the magnesium atom is bound to two hydroxide groups. It has a role as an antacid and a flame retardant.

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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.