Sodium hydroxide

Sodium hydroxide
	Sodium, Na Oxygen, O Hydrogen, H
Names
	IUPAC name Sodium hydroxide
	Other names Ascarite; Caustic soda; Lye; Soda lye; Sodium hydrate; White caustic;
Identifiers
CAS Number	1310-73-2 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:32145 ;
ChemSpider	14114 ;
ECHA InfoCard	100.013.805
EC Number	215-185-5;
E number	E524 (acidity regulators, ...)
Gmelin Reference	68430
KEGG	D01169 ;
MeSH	Sodium+Hydroxide
PubChem CID	14798;
RTECS number	WB4900000;
UNII	55X04QC32I ;
UN number	1823 (solid); 1824 (solution)
CompTox Dashboard (EPA)	DTXSID0029634 ;
	InChI InChI=1S/Na.H2O/h;1H2/q+1;/p-1 Key: HEMHJVSKTPXQMS-UHFFFAOYSA-M ; InChI=1/Na.H2O/h;1H2/q+1;/p-1 Key: HEMHJVSKTPXQMS-REWHXWOFAM;
	SMILES [OH-].[Na+];
Properties
Chemical formula	NaOH
Molar mass	39.9971 g/mol
Appearance	White, opaque crystals
Odor	odorless
Density	2.13 g/cm3
Melting point	323 °C (613 °F; 596 K)
Boiling point	1,388 °C (2,530 °F; 1,661 K)
Solubility in water	418 g/L (0 °C); 1000 g/L (25 °C); 3370 g/L (100 °C)
Solubility	soluble in glycerol, negligible in ammonia, insoluble in ether, slowly soluble in propylene glycol
Solubility in methanol	238 g/L
Solubility in ethanol	139 g/L
Vapor pressure	<2.4 kPa (20 °C); 0.1 kPa (700 °C)
Acidity (pKa)	13.9 (Na+)
Basicity (pKb)	0.0 (OH−)
Magnetic susceptibility (χ)	−15.8·10−6 cm3/mol (aq.)
Refractive index (nD)	1.3576
Structure
Crystal structure	Orthorhombic, oS8
Space group	Cmcm, No. 63
Lattice constant	a = 0.34013 nm, b = 1.1378 nm, c = 0.33984 nm
Formula units (Z)	4
Thermochemistry
Heat capacity (C)	59.5 J/(mol·K)
Std molar; entropy (S⦵298)	64.4 J/(mol·K)
Std enthalpy of; formation (ΔfH⦵298)	−425.8 kJ/mol
Gibbs free energy (ΔfG⦵)	−379.7 kJ/mol
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H290, H302, H314
Precautionary statements	P280, P305+P351+P338, P310
NFPA 704 (fire diamond)	3 0 1 ALK
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	40 mg/kg (mouse, intraperitoneal); 140 - 340 mg/kg (rat, oral); 1350 mg/kg (rabbit, dermal)
LDLo (lowest published)	500 mg/kg (rabbit, oral)
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 2 mg/m3
REL (Recommended)	C 2 mg/m3
IDLH (Immediate danger)	10 mg/m3
Safety data sheet (SDS)	External SDS
Related compounds
Other anions	Sodium hydrosulfide; Sodium hydride; Sodium oxide;
Other cations	Lithium hydroxide; Potassium hydroxide; Rubidium hydroxide; Caesium hydroxide; Francium hydroxide;
Related compounds	Sodium deuteroxide; Sodium chloroxide;
	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

Sodium hydroxide, also known as lye and caustic soda,^[1]^[2] is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations Na⁺ and hydroxide anions OH⁻.

Sodium hydroxide is a highly corrosive base and alkali that decomposes lipids and proteins at ambient temperatures, and may cause severe chemical burns at high concentrations. It is highly soluble in water, and readily absorbs moisture and carbon dioxide from the air. It forms a series of hydrates NaOH·nH₂O.^[13] The monohydrate NaOH·H₂O crystallizes 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.

As one of the simplest hydroxides, sodium hydroxide is frequently used alongside neutral water and acidic hydrochloric acid to demonstrate the pH scale to chemistry students.^[14]

Sodium hydroxide is used in many industries: in the making of wood pulp and paper, textiles, drinking water, soaps and detergents, and as a drain cleaner. Worldwide production in 2022 was approximately 83 million tons.^[15]

^ ^a ^b "Material Safety Datasheet" (PDF). certified-lye.com. Archived from the original (PDF) on 2008-02-28. Retrieved 2010-02-24.
^ ^a ^b "Material Safety Datasheet 2" (PDF). hillbrothers.com. Archived from the original (PDF) on 2012-08-03. Retrieved 2012-05-20.
^ ^a ^b "Sodium Hydroxide – Compound Summary". Retrieved June 12, 2012.
^ ^a ^b ^c ^d Haynes, p. 4.90
^ Smith, R.M.; Martell, A.E. and Motekaitis, R.J. (2001). "NIST Critical Stability Constants of Metal Complexes". NIST Gaithersburg, MD. Database 46.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Neils, T.L.; Schaertel, S. and Silverstein, T.P. (2024). "The pKa of Water and the Fundamental Laws Describing Solution Equilibria: An Appeal for a Consistent Thermodynamic Pedagogy". Helv. Chim. Acta. 107 (11) e202400103. Bibcode:2024HChAc.107E0103N. doi:10.1002/hlca.202400103.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Haynes, p. 4.135
^ Jacobs, H.; Kockelkorn, J. and Tacke, Th. (1985). "Hydroxide des Natriums, Kaliums und Rubidiums: Einkristallzüchtung und röntgenographische Strukturbestimmung an der bei Raumtemperatur stabilen Modifikation". Z. Anorg. Allg. Chem. 531 (12): 119–124. Bibcode:1985ZAACh.531..119J. doi:10.1002/zaac.19855311217.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Haynes, p. 5.13
^ ^a ^b ^c NIOSH Pocket Guide to Chemical Hazards. "#0565". National Institute for Occupational Safety and Health (NIOSH).
^ Michael Chambers. "ChemIDplus – 1310-73-2 – HEMHJVSKTPXQMS-UHFFFAOYSA-M – Sodium hydroxide [NF] – Similar structures search, synonyms, formulas, resource links, and other chemical information.". nih.gov.
^ "Sodium hydroxide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ Cite error: The named reference siem was invoked but never defined (see the help page).
^ "Examples of Common Laboratory Chemicals and their Hazard Class". Archived from the original on 2018-01-10. Retrieved 2018-01-09.
^ "Caustic Soda Market Size, Growth, Trends & Forecast, 2034".

[msd-1] "Material Safety Datasheet" (PDF). certified-lye.com. Archived from the original (PDF) on 2008-02-28. Retrieved 2010-02-24.

[msd2-2] "Material Safety Datasheet 2" (PDF). hillbrothers.com. Archived from the original (PDF) on 2012-08-03. Retrieved 2012-05-20.

[PubChem-3] "Sodium Hydroxide – Compound Summary". Retrieved June 12, 2012.

[crc-4] Haynes, p. 4.90

[5] Smith, R.M.; Martell, A.E. and Motekaitis, R.J. (2001). "NIST Critical Stability Constants of Metal Complexes". NIST Gaithersburg, MD. Database 46.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[6] Neils, T.L.; Schaertel, S. and Silverstein, T.P. (2024). "The pKa of Water and the Fundamental Laws Describing Solution Equilibria: An Appeal for a Consistent Thermodynamic Pedagogy". Helv. Chim. Acta. 107 (11) e202400103. Bibcode:2024HChAc.107E0103N. doi:10.1002/hlca.202400103.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[7] Haynes, p. 4.135

[8] Jacobs, H.; Kockelkorn, J. and Tacke, Th. (1985). "Hydroxide des Natriums, Kaliums und Rubidiums: Einkristallzüchtung und röntgenographische Strukturbestimmung an der bei Raumtemperatur stabilen Modifikation". Z. Anorg. Allg. Chem. 531 (12): 119–124. Bibcode:1985ZAACh.531..119J. doi:10.1002/zaac.19855311217.{{cite journal}}: CS1 maint: multiple names: authors list (link)

[9] Haynes, p. 5.13

[PGCH-10] NIOSH Pocket Guide to Chemical Hazards. "#0565". National Institute for Occupational Safety and Health (NIOSH).

[11] Michael Chambers. "ChemIDplus – 1310-73-2 – HEMHJVSKTPXQMS-UHFFFAOYSA-M – Sodium hydroxide [NF] – Similar structures search, synonyms, formulas, resource links, and other chemical information.". nih.gov.

[12] "Sodium hydroxide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).

[siem-13] Cite error: The named reference siem was invoked but never defined (see the help page).

[14] "Examples of Common Laboratory Chemicals and their Hazard Class". Archived from the original on 2018-01-10. Retrieved 2018-01-09.

[15] "Caustic Soda Market Size, Growth, Trends & Forecast, 2034".

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