Hypophosphorous acid
Description
Hypophosphorous acid (CAS 6303-21-5), also known as phosphinic acid and commonly abbreviated as HPA, is a reducing acid used across chemical manufacturing, surface treatment, and stabilization processes.
It functions primarily as a strong reducing agent and antioxidant, preventing oxidative degradation in sensitive formulations and enabling metal deposition in industrial finishing applications.
In electroless nickel plating, HPA serves as the reducing agent that drives metal deposition onto non-conductive substrates, making it a process-critical input for electronics and precision component manufacturing.
Pharmaceutical manufacturers use it to prevent discoloration and oxidative breakdown in active ingredient formulations during production and storage. It ensures the stability of sensitive chemical compounds.
In textile and leather processing, it controls unwanted oxidation during dyeing and finishing operations, improving color consistency and product shelf life for high-quality consumer goods.
Water treatment applications rely on HPA for pH regulation and as a reducing agent to manage dissolved oxygen and metal ion activity in complex industrial process water systems.
Hypophosphorous acid is supplied as an aqueous solution, with 50% concentration being the most commercially standard grade. Technical and industrial grades are the primary market offerings for most users.
Pharmaceutical-grade material is available to meet stricter purity requirements for drug manufacturing applications. Bulk liquid supply in IBC containers and drums is the typical packaging format for buyers.
Physical Properties
| Melting Point | 26.5 °C |
| Boiling Point | 108 °C (759.8513 mmHg) |
| Density | 1.479 g/cm³ @ Temp: 20 °C |
| Appearance | colourless liquid |
| Color | Colorless |
| Form | hygroscopic crystals or colorless oily liquid |
| Water Solubility | SOLUBLE |
| Vapor Pressure | <17 mmHg ( 20 °C) |
| pH | pKa1= 1.00(25℃) |
Safety & Handling (Learn More)
Trade & Regulatory
| HS Code | 28111990 |
| UN Number | 3264 |
| ADR Class | 8 |
| Packing Group | III |
| Storage Class | 8B - Non-combustible corrosive hazardous materials |
| WGK (Germany) | 1 |
Documentation
Other Names
phosphinic acid|Acid, Phosphinic|RefChem:929168|8B1RL9B4ZJ|Hydroxyphosphine oxide|Phosphine oxide, hydroxy-|Phosphonous acid|HPA
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