Phosphoric acid

Athanor · official

H₃O₄P · 97.995 g/mol

Also called Pi, orthophosphate, E338

Nucleic acid parts

Open in Athanor

Drawn from its SMILES with RDKit

DangerCauses severe skin burns and eye damage

Names and identifiers

IUPAC name: phosphoric acid
Synonyms: Pi, orthophosphate, E338
+ 37 more
ORTHOPHOSPHORIC ACID, o-Phosphoric acid, Wc-reiniger, Acidum phosphoricum, Sonac, Phosphorsaeure, Evits, Acide phosphorique, Phosphoricum acidum, Acido fosforico, Phosphorsaeureloesungen, FEMA No. 2900, Fosforzuuroplossingen, Vococid, White phosphoric acid, Amberphos 54, DTXSID5024263, NSC-80804, E4GA8884NN, INS NO.338, INS-338, Y-11A06, DTXCID804263, E 338, E-338, CHEBI:26078, NSC80804, Phosphoric acid (aqueous), Naturasil Acne, Pre-Sept Activator, Naturasil Bite Relief, Phosphoricum acidum 6C, RefChem:6669, Naturasil Cherry Angiomas, Phosphoricum acidum 200C, Phosphoricum Acidum Kit Refill, Bestmade Natural Products Phos Acid
Molecular formula: H₃O₄P
Empirical formula: H₃O₄P
Molecular weight: 97.995 g/mol
Exact mass: 97.97690
CAS number: 7664-38-2
PubChem CID: 1004
Canonical SMILES: OP(=O)(O)O
Isomeric SMILES: OP(=O)(O)O
InChI: InChI=1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)
InChIKey: NBIIXXVUZAFLBC-UHFFFAOYSA-N
Molfile

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

Physical properties

TemperaturePressureDensity

Appearance: Thick, colorless crystalline solid [Note: Often used in an aqueous solution][6]
8 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
– Phosphoric acid appears as a clear colorless liquid or transparent crystalline solid. The pure solid melts at 42.35 °C and has a density of 1.834 g / cm3. Liquid is usually an 85% aqueous solution. Shipped as both a solid and liquid. Corrosive to metals and tissue. Used in making fertilizers and detergents and in food processing. [1] CAMEO Chemicals
– Large Crystals; CBI; Dry Powder; Other Solid; Liquid; Dry Powder; Liquid; Liquid; Other Solid [2] EPA Chemical Data Reporting (CDR)
– HYGROSCOPIC COLOURLESS CRYSTALS. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– CLEAR COLOURLESS ODOURLESS LIQUID. [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Thick, colorless, odorless, crystalline solid. [4] Occupational Safety and Health Administration (OSHA)
– Thick, colorless, odorless, crystalline solid. [Note: Often used in an aqueous solution.] [5] The National Institute for Occupational Safety and Health (NIOSH)
– Colorless, sparkling liquid or transparent, crystalline solid, depending on concentration and temperature. At 20 °C the 50% and 75% strengths are mobile liquids, the 85% is of syrupy consistency; the 100% acid is in the form of crystals. [6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 984
–shown Thick, colorless crystalline solid [Note: Often used in an aqueous solution] [6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards & Other Databases CD-ROM. 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 Jul 14, 2011: https://www.
Odor: Odorless[6]
Melting point: 42.4 °C[7]
6 values
5 of 5 sources agree on it (most common value).
Value As written Source
42 °C 108 °F (NIOSH, 2024) [1] CAMEO Chemicals
42 °C 42 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
21.1 °C 21.1 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
42 °C 108 °F [4] Occupational Safety and Health Administration (OSHA)
42.4 °Cshown 42.4 °C [7] PAC Chemical Database, U.S. Department of Energy
42 °C 108 °F [5] The National Institute for Occupational Safety and Health (NIOSH)
7 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Boiling point: 213 °C (415 °F)[5]
5 values
2 of 4 sources agree on it (most common value).
Value As written Source
> 130 °C greater than 266 °F at 760 mmHg (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.
158 °C 158 °C [3] ILO-WHO International Chemical Safety Cards (ICSCs)
213 °C 415 °F [4] Occupational Safety and Health Administration (OSHA)
407 °C 407 °C @760 [mm Hg] [7] PAC Chemical Database, U.S. Department of Energy
213 °Cshown 415 °F [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.
Density: 1.87 (pure) 1.33 (50% solution)[4]
4 values
4 of 4 sources agree on it (most common value).
Value As written Source
– 1.892 at 77 °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.
– 1.9 g/cm³ [3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown 1.87 (pure) 1.33 (50% solution) [4] Occupational Safety and Health Administration (OSHA)
– 1.834 @ 18°C [7] PAC Chemical Database, U.S. Department of Energy
6 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Solubility in water: Solubility in water: miscible[3]
4 values
From ILO-WHO International Chemical Safety Cards (ICSCs), the most authoritative source here.
Value As written Source
– Miscible (NIOSH, 2024) [1] CAMEO Chemicals
–shown Solubility in water: miscible [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Solubility in water: very soluble [3] ILO-WHO International Chemical Safety Cards (ICSCs)
– Miscible [5] The National Institute for Occupational Safety and Health (NIOSH)
log P: -0.77 (estimated)[3]
Vapor pressure: 0.0285 [mmHg] @20 °C[7]
2 values
Sources disagree; from PAC Chemical Database, U.S. Department of Energy, the most authoritative.
Value As written Source
2.2 mmHg Vapor pressure, kPa at 20 °C: 0.29 [3] ILO-WHO International Chemical Safety Cards (ICSCs)
0.0285 mmHgshown 0.0285 [mm Hg] @20 °C [7] PAC Chemical Database, U.S. Department of Energy
13 more values were reported but failed the checks (unreadable or out of range), so they are not shown.
Autoignition temperature: Reported, but no value passed the checks.
The value and why
Not flammable (USCG, 1999) (could not be read; source [1])
Viscosity: 3.86 mPa.s (40% solution at 20 °C).[6]

Value	As written	Source
–	Phosphoric acid appears as a clear colorless liquid or transparent crystalline solid. The pure solid melts at 42.35 °C and has a density of 1.834 g / cm3. Liquid is usually an 85% aqueous solution. Shipped as both a solid and liquid. Corrosive to metals and tissue. Used in making fertilizers and detergents and in food processing.	[1] CAMEO Chemicals
–	Large Crystals; CBI; Dry Powder; Other Solid; Liquid; Dry Powder; Liquid; Liquid; Other Solid	[2] EPA Chemical Data Reporting (CDR)
–	HYGROSCOPIC COLOURLESS CRYSTALS.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	CLEAR COLOURLESS ODOURLESS LIQUID.	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Thick, colorless, odorless, crystalline solid.	[4] Occupational Safety and Health Administration (OSHA)
–	Thick, colorless, odorless, crystalline solid. [Note: Often used in an aqueous solution.]	[5] The National Institute for Occupational Safety and Health (NIOSH)
–	Colorless, sparkling liquid or transparent, crystalline solid, depending on concentration and temperature. At 20 °C the 50% and 75% strengths are mobile liquids, the 85% is of syrupy consistency; the 100% acid is in the form of crystals.	[6] Hazardous Substances Data Bank (HSDB)cites Lewis, R.J. Sr.; Hawley's Condensed Chemical Dictionary 15th Edition. John Wiley & Sons, Inc. New York, NY 2007., p. 984
–shown	Thick, colorless crystalline solid [Note: Often used in an aqueous solution]	[6] Hazardous Substances Data Bank (HSDB)cites NIOSH. NIOSH Pocket Guide to Chemical Hazards & Other Databases CD-ROM. 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 Jul 14, 2011: https://www.

Value	As written	Source
42 °C	108 °F (NIOSH, 2024)	[1] CAMEO Chemicals
42 °C	42 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
21.1 °C	21.1 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
42 °C	108 °F	[4] Occupational Safety and Health Administration (OSHA)
42.4 °Cshown	42.4 °C	[7] PAC Chemical Database, U.S. Department of Energy
42 °C	108 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
> 130 °C	greater than 266 °F at 760 mmHg (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.
158 °C	158 °C	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
213 °C	415 °F	[4] Occupational Safety and Health Administration (OSHA)
407 °C	407 °C @760 [mm Hg]	[7] PAC Chemical Database, U.S. Department of Energy
213 °Cshown	415 °F	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
–	1.892 at 77 °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.
–	1.9 g/cm³	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–shown	1.87 (pure) 1.33 (50% solution)	[4] Occupational Safety and Health Administration (OSHA)
–	1.834 @ 18°C	[7] PAC Chemical Database, U.S. Department of Energy

Value	As written	Source
–	Miscible (NIOSH, 2024)	[1] CAMEO Chemicals
–shown	Solubility in water: miscible	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Solubility in water: very soluble	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
–	Miscible	[5] The National Institute for Occupational Safety and Health (NIOSH)

Value	As written	Source
2.2 mmHg	Vapor pressure, kPa at 20 °C: 0.29	[3] ILO-WHO International Chemical Safety Cards (ICSCs)
0.0285 mmHgshown	0.0285 [mm Hg] @20 °C	[7] PAC Chemical Database, U.S. Department of Energy

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: 5
Rings: 0
Aromatic rings: 0
Fraction sp³ carbons (Fsp3): 0
H-bond donors: 3
H-bond acceptors: 1 computed here · PubChem 4
Rotatable bonds: 0
TPSA (Å²): 77.8
Formal charge: 0
XLogP3: -2.1 PubChem
Complexity: 49 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C3 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

H3.09%
O65.31%
P31.61%

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: -0.93 Crippen (Wildman and Crippen 1999)
log S (water solubility): 0.14 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 2.61 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 97.99
log P ≤ 5 (Crippen): -0.93
H-bond donors ≤ 5: 3
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 (3)

[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 4293) of reports.
[9] European Chemicals Agency (ECHA) · 4,293 reports · DangerH290, H302, H314, H318

Exposure limits

PEL-TWA (8-Hour Time Weighted Average): 1 mg/m³[4]
PEL: TWA 1 mg/m3 See Appendix G[5]
REL-STEL (Short Term Exposure Limit): 3 mg/m³[4]
REL: TWA 1 mg/m3 ST 3 mg/m3[5]
TLV: 1 mg/m[3]
TLV-TWA (Time Weighted Average): 1 mg/m³ [1992][4]

First aid

Excerpt from NIOSH Pocket Guide for Phosphoric acid: 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]
(General first aid procedures) 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.[5]

Storage

Dry. Well closed. Separated from food and feedstuffs and incompatible materials. See Chemical Dangers. Store in an area without drain or sewer access.[3]
Separated from food and feedstuffs and incompatible materials. See Chemical Dangers. Store only in original container. Store in an area without drain or sewer access.[3]
Store in cool, dry, well-ventilated location. Separate from alkalies and most metals.[6]

Incompatibilities

Reacts with metals to liberate flammable hydrogen gas.[6]
With sodium tetrahydroborate: Interaction of sodium and other tetrahydroborates with anhydrous acids (phosphoric acid) to generate diborane is very exothermic, and may be dangerously violent with rapid mixing.[6]
Heat generated with: Alcohols and glycols; Aldehydes; Amides; Amines; Azo-compounds; Carbamates; Caustics; Esters; Ketones; Phenols and cresols; Organophosphates; Epoxides; Combustible materials; Explosives; Unsaturated halides; And organic peroxides.[6]
Formation of flammable gases with: Aldehydes; Cyanides; Mercaptans; and sulfides. Formation of toxic fumes with: Cyanides; Fluorides; Halogenated organics; Sulfides; And organic peroxides.[6]

Safety data sheets on the supplier’s page: Sigma-Aldrich, Aladdin Scientific, J&H Chemical Co.,ltd.

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

Spectra

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
[12]Human Metabolome Database (HMDB) · Linked only · via PubChem · retrieved 2026-10-14
[13]MassBank of North America (MoNA) · CC BY 4.0 · via PubChem · retrieved 2026-10-14
[14]NIST Mass Spectrometry Data Center · Linked only · via PubChem · retrieved 2026-10-14
[15]MassBank Europe · 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.