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Inorganic acids

Phosphorous acid

Also known as Orthophosphorus acid, Dihydroxyphosphine oxide, Trihydroxyphosphine

CAS 10294-56-1Formula H3O3PMolar mass 82.00 g/molEC 233-663-1
GHS signal word: Danger. Pictograms: Corrosive, Harmful or irritant 110 suppliers listed
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Phosphorous acid chemical structure, H3O3P, CAS 10294-56-1
2D chemical structure

Key facts

What buyers check first

All properties
CAS number
10294-56-1
Formula
H3O3P
Physical form
Liquid
HS code
281119
Category
Inorganic acids
UN number
UN 2834
Illustrative photo, closed blue steel drums of liquid in a chemical plant
Typical packagingIllustrative packaging image, not the actual product

What is Phosphorous acid?

Plain description, key identifiers and synonyms

Phosphorous acid is a phosphorus oxoacid. It is a conjugate acid of a dihydrogenphosphite. It is a tautomer of a phosphonic acid.

Identifiers

Registry numbers, names and line notations, tap to copy

IUPAC name
phosphorous acid
CAS number
10294-56-1 CAS number cross-checkedOther or deprecated CAS: 14901-63-4, 14939-26-5
EC number
233-663-1
Molecular formula
H3O3P
InChIKey
OJMIONKXNSYLSR-UHFFFAOYSA-N
InChI
InChI=1S/H3O3P/c1-4(2)3/h1-3H
SMILES (canonical and isomeric)
OP(O)O

Synonyms

  • Orthophosphorus acid
  • Dihydroxyphosphine oxide
  • Trihydroxyphosphine
  • Phosphorane, trihydroxy-
  • Orthophosphorous acid
  • trioxophosphate
  • Phophorous acid
  • trioxidophosphate
  • Phosphorous-acid-
  • Pamidronate EP Impurity C
  • Phosphorous acid [UN2834] [Corrosive]

Physical and chemical properties

Measured values and descriptors computed from the structure

Physical and chemical properties

Measured values, check the supplier specification for your grade

Physical form
Liquidexp.

Values vary by grade. Ask suppliers for the COA or TDS of the batch you buy.

Computed descriptors

Calculated from the structure, useful for screening and formulation

Molecular weight
82.00 g/molcalc.
Exact mass
81.982 Dacalc.
LogP (octanol/water)
-0.81calc.
Topological polar surface area
60.69 Ųcalc.
Hydrogen bond donors
3calc.
Hydrogen bond acceptors
3calc.
Rotatable bonds
0calc.
Heavy atoms
4calc.
Rings
0calc.
Aromatic rings
0calc.
Fraction sp3 carbons
0calc.
Formal charge
0calc.
Stereocentres
0calc.

Calculated for screening. Confirm critical figures with the supplier.

Safety and hazards

GHS classification summary, not a safety data sheet

GHS signal word
Danger
GHS05: Corrosive
Corrosive
GHS07: Harmful or irritant
Harmful or irritant

Hazard statements

  • H302Harmful if swallowed.
  • H314Causes severe skin burns and eye damage.
Precautionary statements (15)
  • P260Do not breathe dust, fume, gas, mist, vapours or spray.
  • P264Wash skin thoroughly after handling.
  • P270Do not eat, drink or smoke when using this product.
  • P280Wear protective gloves, protective clothing, eye protection and face protection.
  • P301 + P317If swallowed: Get medical help.
  • P301 + P330 + P331If swallowed: Rinse mouth. Do not induce vomiting.
  • P302 + P361 + P354If on skin: Take off immediately all contaminated clothing. Immediately rinse with water for several minutes.
  • P304 + P340If inhaled: Remove person to fresh air and keep comfortable for breathing.
  • P305 + P354 + P338If in eyes: Immediately rinse with water for several minutes. Remove contact lenses, if present and easy to do. Continue rinsing.
  • P316Get emergency medical help immediately.
  • P321Specific treatment (see supplemental first aid instructions on the label).
  • P330Rinse mouth.
  • P363Wash contaminated clothing before reuse.
  • P405Store locked up.
  • P501Dispose of contents and container in accordance with local regulations.
UN number
UN 2834
Transport hazard class
8
Packing group
III

GHS classification summary, not a safety data sheet (SDS). Classifications can differ by supplier, grade and concentration. Always check the supplier's SDS.

Full safety data and first aid

Phosphorous acid suppliers

Sponsored listings first, then the documented ranking: membership, verification, replies, completeness, freshness and ratings

All 110 suppliers
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Suppliers marked Unclaimed profile have not claimed their profile yet. They are not verified by CompoundList, their offers are price on request and details may have changed, so please confirm them with the supplier. Company representatives can claim a profile with a business email on the company's own website domain. Our team verifies each claim and sends the result by email.

Where suppliers are based

110 suppliers in 15 countries

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Phosphorous acid price

Indicative price range per kg from live supplier offers

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Uses and applications

What the substance is used for, by industry and function

Industrial uses: Stabilizing agent, Anti-scaling agent, Intermediate.

Consumer uses: Lubricating agent, Anti-scaling agent, Stabilizing agent.

Use classes: Oxidants and Oxidant Stabilizers, Safer Chemical Classes.

Roles

  • antifungal agent
  • antimicrobial agent
  • fungicide
  • pesticide

Functional uses

  • Oxidizing agent

Regulatory status

Inventories, regulations and trade controls that list this substance

Europe

  • EU harmonised classification (CLP Annex VI)
    Index no: 015-157-00-0[2]

United States

  • Safer Choice ingredient list (USA)
  • TSCA inventory (USA)
    Status: Active in US commerce

HS code and trade data

Customs classification and reported world trade statistics

Global trade

World import and export statistics for the HS code Phosphorous acid is traded under.

HS 2811.19Indicative HS code

Inorganic acids, other than hydrogen fluoride

World exports in 2024
$494M
+6.5% vs 2023, imports $458M
2019 to 2024
Top exporters
  1. China24.9%
  2. Israel16.0%
  3. Jordan * partner reported11.7%
Top importers
  1. China29.3%
  2. United States16.2%
  3. Germany7.0%

* Partner reported figures, a lower bound.

Reported customs values in USD, not prices.Full trade data

The HS code shown for Phosphorous acid is indicative (it was assigned by structure rules). Confirm the classification with your customs broker before shipping.

Frequently asked questions

Quick answers about Phosphorous acid, based on the data on this page

What is Phosphorous acid?

Phosphorous acid is a phosphorus oxoacid. It is a conjugate acid of a dihydrogenphosphite. It is a tautomer of a phosphonic acid.

What is the CAS number of Phosphorous acid?

The CAS registry number of Phosphorous acid is 10294-56-1. Other or deprecated CAS numbers: 14901-63-4, 14939-26-5.

What is the molecular formula and weight of Phosphorous acid?

The molecular formula of Phosphorous acid is H3O3P and its molar mass is 82.00 g/mol.

What is Phosphorous acid used for?

Industrial uses: Stabilizing agent, Anti-scaling agent, Intermediate. Consumer uses: Lubricating agent, Anti-scaling agent, Stabilizing agent. Use classes: Oxidants and Oxidant Stabilizers, Safer Chemical Classes.

Is Phosphorous acid hazardous?

Phosphorous acid carries the GHS signal word "Danger". Main hazards: harmful if swallowed, causes severe skin burns and eye damage. This summary is not an SDS, always read the supplier safety data sheet.

What is the HS code of Phosphorous acid?

Phosphorous acid is usually classified under HS code 281119 (II. INORGANIC ACIDS AND INORGANIC OXYGEN COMPOUNDS OF NON-METALS, other). This is indicative, confirm it with your customs broker before shipping.

Where can I buy Phosphorous acid?

CompoundList lists 110 suppliers of Phosphorous acid in China, United States, India, Turkey and 11 more. Send one free request to get and compare quotes. Your contact details stay private until you accept a quote.

Where can I buy Phosphorous acid in India?

15 suppliers in India list Phosphorous acid on CompoundList. Filter the suppliers list by country and send a request to compare prices, grades and delivery times.

What is the price of Phosphorous acid?

Suppliers quote Phosphorous acid on request because prices depend on grade, purity, quantity and destination. A free request on CompoundList gets you several quotes to compare.

Guides for buyers

Practical guides that help when you source, ship or handle Phosphorous acid

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Data last updated 7 Oct 2026. Details may have changed, please confirm them with the supplier. Report an error on this page
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