NaOH

Sodium hydroxide

Names
Preferred IUPAC name Sodium hydroxide
Systematic IUPAC name Sodium oxidanide
Other names Caustic soda Lye Ascarite White caustic Sodium hydrate
Identifiers
CAS Number	1310-73-2 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:32145 Y
ChemSpider	14114 Y
ECHA InfoCard	100.013.805
EC Number	215-185-5
E number	E524 (acidity regulators, ...)
Gmelin Reference	68430
KEGG	D01169 Y
MeSH	Sodium+Hydroxide
PubChem CID	14798
RTECS number	WB4900000
UNII	55X04QC32I Y
UN number	1824
InChI InChI=1S/Na.H2O/h;1H2/q+1;/p-1 Y Key: HEMHJVSKTPXQMS-UHFFFAOYSA-M Y InChI=1/Na.H2O/h;1H2/q+1;/p-1 Key: HEMHJVSKTPXQMS-REWHXWOFAM
SMILES O[Na]
Properties
Chemical formula	NaOH
Molar mass	39.9971 g mol−1
Appearance	White, waxy, opaque crystals
Odor	odorless
Density	2.13 g/cm3
Melting point	318 °C (604 °F; 591 K)
Boiling point	1,388 °C (2,530 °F; 1,661 K)
Solubility in water	418 g/L (0 °C) 1110 g/L (20 °C) 3370 g/L (100 °C)
Solubility	soluble in glycerol negligible in ammonia insoluble in ether
Solubility in methanol	238 g/L
Solubility in ethanol	<<139 g/L
Vapor pressure	<2.4 kPa (at 20 °C)
Basicity (pKb)	−0.93(NaOH(aq) = Na+ + OH–)
Magnetic susceptibility (χ)	−16.0·10−6 cm3/mol
Refractive index (nD)	1.3576
Thermochemistry
Specific heat capacity (C)	59.66 J/mol K
Std molar entropy (So298)	64 J·mol−1·K−1
Std enthalpy of formation (ΔfHo298)	−427 kJ·mol−1
Gibbs free energy (ΔfG˚)	-380.7 kJ/mol
Hazards
Safety data sheet	External MSDS
GHS pictograms
GHS signal word	Danger
GHS hazard statements	H314
GHS precautionary statements	P280, P305+351+338, P310
EU classification (DSD)	C
R-phrases	R35
S-phrases	(S1/2), S26, S37/39, S45
NFPA 704	0 3 1 ALK
Lethal dose or concentration (LD, LC):
LD50 (median dose)	40 mg/kg (mouse, intraperitoneal)
LDLo (lowest published)	500 mg/kg (rabbit, oral)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 2 mg/m3
REL (Recommended)	C 2 mg/m3
IDLH (Immediate danger)	10 mg/m3
Related compounds
Other anions	Sodium hydrosulfide
Other cations	Caesium hydroxide Lithium hydroxide Potassium hydroxide Rubidium hydroxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Lye
Ascarite
White caustic

Lithium hydroxide
Potassium hydroxide
Rubidium hydroxide

Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with formula NaOH. It is a white solid, a salt (ionic compound), consisting of sodium cations Na+
and hydroxide anions OH−
.

Sodium hydroxide is a highly caustic base and alkali, that decomposes proteins at ordinary ambient temperatures and may cause severe chemical burns. It is highly soluble in water and readily absorbs moisture and carbon dioxide from the air. It forms a series of hydrates NaOH·nH
2O.. The monohydrate NaOH·H
2O cystallizes from water solutions between 12.3 and 61.8 °C. The commercially available "sodium hydroxide" is often this monohydrate, and published data may refer to it instead of the anhydrous compound.