Sodium hydroxide

Athanor · official

HNaO · 39.997 g/mol

Also called caustic soda, lye, NaOH, E524

Inorganic

Open in Athanor

Drawn from its SMILES with RDKit

DangerCauses severe skin burns and eye damage

Names and identifiers

IUPAC name: sodium hydroxide
Synonyms: caustic soda, lye, NaOH
+ 39 more
E524, Caustic soda, Sodium hydrate, Aetznatron, Soda lye, White caustic, Soda, caustic, Natriumhydroxid, Rohrputz, Plung, Collo-Grillrein, Collo-Tapetta, Fuers Rohr, Rohrreiniger Rofix, Hydroxyde de sodium, Sodium hydroxide (Na(OH)), Natriumhydroxyde, Soda, hydrate, Sodium hydroxide dimer, Natrium causticum, Soda, kaustische, Lewis-red devil lye, Sodio(idrossido di), Sodium hydroxide (Na2(OH)2), Stamperprep, Caustic soda, liquid, Sodium(hydroxyde de), Tosoh pearl, Promoter 3308b, Natrii hydroxydum, NSC-135799, DTXSID0029634, INS-524, 55X04QC32I, E-524, CHEBI:32145, Hydroxide, Sodium, RefChem:117, DTXCID609634
Molecular formula: HNaO
Empirical formula: HNaO
Molecular weight: 39.997 g/mol
Exact mass: 39.99251
CAS number: 1310-73-2
PubChem CID: 14798
Canonical SMILES: [OH-].[Na+]
Isomeric SMILES: [OH-].[Na+]
InChI: InChI=1S/Na.H2O/h;1H2/q+1;/p-1
InChIKey: HEMHJVSKTPXQMS-UHFFFAOYSA-M
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Brittle, white, translucent crystalline solid[6]
8 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Sodium hydroxide solution appears as a colorless liquid. More dense than water. Contact may severely irritate skin, eyes, and mucous membranes. Toxic by ingestion. Corrosive to metals and tissue. [1] CAMEO Chemicals
– Sodium hydroxide, solid appears as a white solid. Corrosive to metals and tissue. Used in chemical manufacturing, petroleum refining, cleaning compounds, drain cleaners. [1] CAMEO Chemicals
– Other Solid; Dry Powder; Liquid; Other Solid; CBI; Large Crystals; Dry Powder; Liquid; Large Crystals; Liquid; Liquid [2] EPA Chemical Data Reporting (CDR)
– WHITE HYGROSCOPIC SOLID IN VARIOUS FORMS. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Colorless to white, odorless solid (flakes, beads, granular form). [4] Occupational Safety and Health Administration (OSHA)
– Colorless to white, odorless solid (flakes, beads, granular form). [5] The National Institute for Occupational Safety and Health (NIOSH)
– Colorless to white ... solid (flakes, beads, granular form). [6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Prevention & Control. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from, as of Oct 7, 2011: https://www.cdc.gov/niosh/npg/
–shown Brittle, white, translucent crystalline solid [6] Hazardous Substances Data Bank (HSDB)cites Eggeman T; Kirk-Othmer Encyclopedia of Chemical Technology. (1999-2011). New York, NY: John Wiley & Sons; Sodium Hydroxide. Online Posting Date: 15 April 2011
Odor: ... Odorless ...[6]
Melting point: 318 °C[3]
5 values
4 of 5 sources agree on it (most common value).
Value As written Source
318 °C 604 °F (USCG, 1999) [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
318 °Cshown 318 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
318 °C 605 °F [4] Occupational Safety and Health Administration (OSHA)
323 °C 323 °C [7] PAC Chemical Database, U.S. Department of Energy
318 °C 605 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
Boiling point: 1388 °C[3]
4 values
2 of 4 sources agree on it (most common value).
Value As written Source
1388 °Cshown 1388 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
1390 °C 2534 °F [4] Occupational Safety and Health Administration (OSHA)
1388 °C 1388 °C @760 [mm Hg] [7] PAC Chemical Database, U.S. Department of Energy
1390 °C 2534 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
2 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Density: 2.13 @25 °C[7]
7 values
5 of 6 sources agree on it (most common value).
Value As written Source
– 1.5 at 68 °F (USCG, 1999) - Denser than water [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
– 2.13 at 68 °F (USCG, 1999) - Denser than water [1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
– Density = 2.0 at 15.5 °C [6] Hazardous Substances Data Bank (HSDB)cites Environment Canada; Tech Info for Problem Spills: Sodium Hydroxide (Draft) p.1 (1981)
– 2.1 g/cm³ [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 2.13 [4] Occupational Safety and Health Administration (OSHA)
–shown 2.13 @25 °C [7] PAC Chemical Database, U.S. Department of Energy
– 2.13 [5] The National Institute for Occupational Safety and Health (NIOSH)
1 more value was reported but failed the checks (unreadable or out of range), so it is not shown.
Solubility in water: Solubility in water, g/100ml at 20 °C: 109 (very good)[3]
3 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– 111 % (NIOSH, 2024) [1] CAMEO Chemicals
–shown Solubility in water, g/100ml at 20 °C: 109 (very good) [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– 111% [5] The National Institute for Occupational Safety and Health (NIOSH)
pKa: Reported, but no value passed the checks.
The value and why
SRP4: Completely dissociated (could not be read; source [6])
Vapor pressure: 1.82 × 10⁻²¹ mmHg at 25 °C (extrapolated)[6]
Autoignition temperature: Reported, but no value passed the checks.
The 2 values and why
Not flammable (USCG, 1999) (could not be read; source [1])
Not flammable (USCG, 1999) (could not be read; source [1])
Viscosity: 4.0 cP at 350 °C[6]
Refractive index: 1.421 at 420 °C[6]

Value	As written	Source
–	Sodium hydroxide solution appears as a colorless liquid. More dense than water. Contact may severely irritate skin, eyes, and mucous membranes. Toxic by ingestion. Corrosive to metals and tissue.	[1] CAMEO Chemicals
–	Sodium hydroxide, solid appears as a white solid. Corrosive to metals and tissue. Used in chemical manufacturing, petroleum refining, cleaning compounds, drain cleaners.	[1] CAMEO Chemicals
–	Other Solid; Dry Powder; Liquid; Other Solid; CBI; Large Crystals; Dry Powder; Liquid; Large Crystals; Liquid; Liquid	[2] EPA Chemical Data Reporting (CDR)
–	WHITE HYGROSCOPIC SOLID IN VARIOUS FORMS.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Colorless to white, odorless solid (flakes, beads, granular form).	[4] Occupational Safety and Health Administration (OSHA)
–	Colorless to white, odorless solid (flakes, beads, granular form).	[5] The National Institute for Occupational Safety and Health (NIOSH)
–	Colorless to white ... solid (flakes, beads, granular form).	[6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards. Department of Health & Human Services, Centers for Disease Prevention & Control. National Institute for Occupational Safety & Health. DHHS (NIOSH) Publication No. 2010-168 (2010). Available from, as of Oct 7, 2011: https://www.cdc.gov/niosh/npg/
–shown	Brittle, white, translucent crystalline solid	[6] Hazardous Substances Data Bank (HSDB)cites Eggeman T; Kirk-Othmer Encyclopedia of Chemical Technology. (1999-2011). New York, NY: John Wiley & Sons; Sodium Hydroxide. Online Posting Date: 15 April 2011

Value	As written	Source
318 °C	604 °F (USCG, 1999)	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
318 °Cshown	318 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
318 °C	605 °F	[4] Occupational Safety and Health Administration (OSHA)
323 °C	323 °C	[7] PAC Chemical Database, U.S. Department of Energy
318 °C	605 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
1388 °Cshown	1388 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
1390 °C	2534 °F	[4] Occupational Safety and Health Administration (OSHA)
1388 °C	1388 °C @760 [mm Hg]	[7] PAC Chemical Database, U.S. Department of Energy
1390 °C	2534 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	1.5 at 68 °F (USCG, 1999) - Denser than water	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–	2.13 at 68 °F (USCG, 1999) - Denser than water	[1] CAMEO Chemicalscites U.S. Coast Guard. 1999. Chemical Hazard Response Information System (CHRIS) - Hazardous Chemical Data. Commandant Instruction 16465.12C. Washington, D.C.: U.S. Government Printing Office.
–	Density = 2.0 at 15.5 °C	[6] Hazardous Substances Data Bank (HSDB)cites Environment Canada; Tech Info for Problem Spills: Sodium Hydroxide (Draft) p.1 (1981)
–	2.1 g/cm³	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	2.13	[4] Occupational Safety and Health Administration (OSHA)
–shown	2.13 @25 °C	[7] PAC Chemical Database, U.S. Department of Energy
–	2.13	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	111 % (NIOSH, 2024)	[1] CAMEO Chemicals
–shown	Solubility in water, g/100ml at 20 °C: 109 (very good)	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	111%	[5] The National Institute for Occupational Safety and Health (NIOSH)

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 2
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 0 computed here · PubChem 1
H-bond acceptors: 1
Rotatable bonds: 0
TPSA (Å²): 30 computed here · PubChem 1
Formal charge: 0
Complexity: 2 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C∞v of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

H2.52%
Na57.48%
O40.00%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: -3.17 Crippen (Wildman and Crippen 1999)
log S (water solubility): 1.91 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 8.49 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 40
log P ≤ 5 (Crippen): -3.17
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 1

Passes all four rules.

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Harmonized EU classification (CLP Annex VI). Source [8].

Corrosive

NFPA 704[6]

H314Causes severe skin burns and eye damage

Precautionary statements: P260, P264, P280, P301+P330+P331, P302+P361+P354, P304+P340, P305+P354+P338, P316, P321, P363, P405, P501

View all classifications (4)

[8] Regulation (EC) No 1272/2008 of the European Parliament and of the Council · DangerH314
[9] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for < 0.1% (4 of 6949) of reports.
[9] European Chemicals Agency (ECHA) · 6,949 reports · DangerH290, H315, H318, H319
[9] European Chemicals Agency (ECHA) · 2 reports · DangerH290, H314, H318

Exposure limits

PEL-TWA (8-Hour Time Weighted Average): 2 mg/m³[4]
PEL: TWA 2 mg/m3 See Appendix G[5]
REL: C 2 mg/m3[5]
TLV: 2 mg/m[3]
TLV-C (Ceiling): 2 mg/m³ [1992][4]
IDLH: 10 mg/m3 [From npg: Sodium hydroxide] (NIOSH, 2024)[1]

First aid

(Act quickly) eyes: Flush with water at once for at least 15 min. Skin: Flush with water, then rinse with dilute vinegar (acetic acid). Ingestion: Give water and milk. Do NOT induce vomiting. Call physician at once, even when injury seems to be slight. (USCG, 1999)[1]
Excerpt from NIOSH Pocket Guide for Sodium hydroxide: Eye: Irrigate immediately - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately. Skin: Water flush immediately - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water.[1]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[10]
General First Aid: · Call 911 or emergency medical service. · Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination. · Move victim to fresh air if it can be done safely. · Administer oxygen if breathing is difficult. · If victim is not breathing: -- DO NOT perform mouth-to-mouth resuscitation; the victim may have ingested or inhaled the substance. -- If equipped and pulse detected, wash face and mouth, then give artificial respiration using a proper respiratory medical device (bag-valve mask, pocket mask equipped…[10]

Storage

Separated from food and feedstuffs, strong acids and metals. Store only in original container. Dry. Well closed. Store in an area without drain or sewer access.[3]
Containers should BE stored IN rooms WITH trapped floor drains towards which floors should BE slanted. Where floor drains ARE NOT provided, curbs OR drained gutter, covered WITH ... Grill, should BE constructed @ DOOR openings.[6]
Store in a cool, dry, well-ventilated location. Separate from organic and oxidizing materials, acids, metal powders. Immediately remove and properly dispose of any spilled material.[6]

Incompatibilities

Crude hydroquinone WAS pumped INTO sodium hydroxide storage TANK BY mistake. THE hydroquinone liquor AT 85 °C decomp rapidly IN THE presence OF THE sodium hydroxide resulting IN overflow OF TANK & evolution OF considerable amount OF HEAT.[6]
Much heat is evolved when the solid material is dissolved in water. Therefore, cold water and caution must be used for this process.[6]
Caustic solutions generate heat when further diluted with water. With concentrations of 40% or greater, the heat generated can raise the temperature above the boiling point, resulting in sporadic, dangerous eruptions of the solution.[6]
For more Hazardous Reactivities and Incompatibilities (Complete) data for sodium hydroxide (32 total), please visit the HSDB record page.[6]

Safety data sheets on the supplier’s page: Glentham Life Sciences Ltd., Thermo Fisher Scientific, VladaChem.

Always read the supplier’s safety data sheet before working with it.

Spectra

ATR-IRSpectraBase

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]CAMEO Chemicals · Public domain (NOAA) · via PubChem · retrieved 2026-10-14
[2]EPA Chemical Data Reporting (CDR) · Public domain (US EPA) · via PubChem · retrieved 2026-10-14
[3]ILO-WHO International Chemical Safety Cards (ICSCs) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[4]Occupational Safety and Health Administration (OSHA) · Public domain (US DOL) · via PubChem · retrieved 2026-10-14
[5]The National Institute for Occupational Safety and Health (NIOSH) · Public domain (US CDC) · via PubChem · retrieved 2026-10-14
[6]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[7]PAC Chemical Database, U.S. Department of Energy · Public domain (US DOE) · via PubChem · retrieved 2026-10-14
[8]Regulation (EC) No 1272/2008 of the European Parliament and of the Council · EU reuse policy, CC BY 4.0 · via PubChem · retrieved 2026-10-14
[9]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[10]Emergency Response Guidebook (ERG) · Public domain (US DOT) · via PubChem · retrieved 2026-10-14
[11]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.