Inorganic Acids & Bases
REACH
Phosphonic acid
CAS Number
13598-36-2
EC Number
237-066-7
What is Phosphonic acid?
Phosphonic acid (CAS 13598-36-2) is an inorganic phosphorus-based acid used industrially as a pH regulator, reducing agent, and stabilizer.
Where is Phosphonic acid used?
- Water treatment: pH adjustment agent and scale-inhibition precursor
- Industrial cooling and boiler systems: corrosion control
- Textile and paper processing: bath acidity management during dyeing and bleaching
- Agriculture: building block or acidulant in phosphonate-based fungicides and fertilizer adjuvants
- Pharmaceutical manufacturing: reagent and intermediate in API synthesis
- It supports processes requiring controlled acidic conditions without introducing strong oxidizing byproducts.
Commercial specifications
- Aqueous solution, concentration typically around 50% by weight for industrial use
- Technical grade standard; higher-purity specifications available for pharmaceutical intermediate requirements
- Packaging: drums and intermediate bulk containers
Other Names (Synonyms)
RefChem:6132|Phosphorus trihydroxide|Dihydroxyphosphine oxide|Phosphorous acid
What are the physical properties of Phosphonic acid?
Melting Point ~73 °C (approx)
Boiling Point 200 °C
Density 1.651 g/mL at 25 °C(lit.)
Flash Point 200°C
Appearance white crystalline solid
Color White
Form Crystals
Water Solubility SOLUBLE
Vapor Pressure 0.001Pa at 20℃
pH pKa1= 1.10, pKa2 = 6.33(25℃)
How is Phosphonic acid classified and handled safely? Learn More
Danger
GHS05· Corrosive GHS07· Irritant
Hazard Statements
H290 May be corrosive to metals
H302 Harmful if swallowed
H314 Causes severe skin burns and eye damage
H318 Causes serious eye damage
H335 May cause respiratory irritation
Precautionary Statements
P234 Keep only in original packaging.
P260 Do not breathe dust/fume/gas/mist/vapours/spray.
P261 Avoid breathing dust/fume/gas/mist/vapours/spray.
P264 Wash … thoroughly after handling.
Which trade and regulatory codes apply to Phosphonic acid?
HS Code 28092019
UN Number 2834
ADR Class 8
Packing Group III
Storage Class 8A - Combustible corrosive hazardous materials
WGK (Germany) 1