Phosphonic acid
Description
Phosphonic acid (CAS 13598-36-2) is an inorganic phosphorus-based acid used industrially as a pH regulator, reducing agent, and stabilizer across water treatment, agriculture, and specialty chemical manufacturing.
Its reducing character makes it effective in processes requiring controlled acidic conditions without introducing strong oxidizing byproducts. In water treatment, it functions as a pH adjustment agent and scale-inhibition precursor.
It supports corrosion control programs in industrial cooling and boiler systems. Textile and paper processors use it to manage bath acidity during dyeing and bleaching operations, where consistent pH control directly affects product quality.
In agriculture, it serves as a building block or acidulant in formulating phosphonate-based fungicides and fertilizer adjuvants. Pharmaceutical manufacturers use it as a reagent and intermediate in synthesizing active pharmaceutical ingredients.
These applications require controlled reducing conditions. Phosphonic acid is supplied as an aqueous solution, with concentration typically ranging around 50% by weight for industrial use.
Technical grade is the standard commercial offering, though higher-purity specifications are available to meet pharmaceutical intermediate requirements. Packaging options typically include drums and intermediate bulk containers.
Physical Properties
| 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℃) |
Safety & Handling (Learn More)
Trade & Regulatory
| HS Code | 28092019 |
| UN Number | 2834 |
| ADR Class | 8 |
| Packing Group | III |
| Storage Class | 8A - Combustible corrosive hazardous materials |
| WGK (Germany) | 1 |
Documentation
Other Names
RefChem:6132|Phosphorus trihydroxide|Dihydroxyphosphine oxide|Phosphorous acid
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