Magnesium hydroxide

Magnesium hydroxide
Names
	IUPAC name Magnesium hydroxide
	Other names Magnesium dihydroxide; Milk of magnesia;
Identifiers
CAS Number	1309-42-8 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:6637 ;
ChEMBL	ChEMBL1200718 ;
ChemSpider	14107 ;
DrugBank	DB09104;
ECHA InfoCard	100.013.792
EC Number	215-170-3;
E number	E528 (acidity regulators, ...)
Gmelin Reference	485572
KEGG	C07876;
PubChem CID	14791;
RTECS number	OM3570000;
UNII	NBZ3QY004S ;
CompTox Dashboard (EPA)	DTXSID4049662 ;
	InChI InChI=1S/Mg.2H2O/h;21H2/q+2;;/p-2 Key: VTHJTEIRLNZDEV-UHFFFAOYSA-L ; InChI=1/Mg.2H2O/h;21H2/q+2;;/p-2 Key: VTHJTEIRLNZDEV-NUQVWONBAW;
	SMILES [Mg+2].[OH-].[OH-];
Properties
Chemical formula	Mg(OH)2
Molar mass	58.3197 g/mol
Appearance	White solid
Odor	Odorless
Density	2.3446 g/cm3
Melting point	350 °C (662 °F; 623 K) decomposes
Solubility in water	0.00064 g/100 mL (25 °C); 0.004 g/100 mL (100 °C);
Solubility product (Ksp)	5.61×10−12
Magnetic susceptibility (χ)	−22.1×10−6 cm3/mol
Refractive index (nD)	1.559
Structure
Crystal structure	Hexagonal, hP3
Space group	P3m1 No. 164
Lattice constant	a = 0.312 nm, c = 0.473 nm
Thermochemistry
Heat capacity (C)	77.03 J/mol·K
Std molar; entropy (S⦵298)	64 J·mol−1·K−1
Std enthalpy of; formation (ΔfH⦵298)	−924.7 kJ·mol−1
Gibbs free energy (ΔfG⦵)	−833.7 kJ/mol
Pharmacology
ATC code	A02AA04 (WHO) G04BX01 (WHO)
Hazards
	GHS labelling:
Pictograms
Signal word	Warning
Hazard statements	H315, H319, H335
Precautionary statements	P261, P280, P304+P340, P305+P351+P338, P405, P501
NFPA 704 (fire diamond)	1 0 0
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	8500 mg/kg (rat, oral)
Safety data sheet (SDS)	External MSDS
Related compounds
Other anions	Magnesium oxide
Other cations	Beryllium hydroxide; Calcium hydroxide; Strontium hydroxide; Barium hydroxide;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Magnesium hydroxide is an inorganic compound with the chemical formula Mg(OH)₂. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (K_sp = 5.61×10⁻¹²). Magnesium hydroxide is a common component of antacids, such as milk of magnesia.