Etidronic Acid
HEDP, 1-Hydroxyethylidene-1,1-diphosphonic acid.
- CAS
- 2809-21-4
- EC
- 220-552-8
- Sectors
- Water & Wastewater Treatment, Home Care & Industrial Cleaning
Etidronic Acid (CAS 2809-21-4), also known as HEDP, is an organophosphonate chelating agent built on a hydroxyethylidene diphosphonic structure, supplied as a light beige powder that sequesters calcium, magnesium and iron ions and inhibits carbonate and sulfate scale in cooling water systems and detergent formulations. It is typically supplied as a 60% aqueous solution or as a solid powder for specific formulations.
It exhibits excellent sequestration properties for calcium, magnesium, and iron ions, even at high temperatures. It is highly stable under high pH conditions, making it superior to polyphosphates in industrial cooling systems.
This Technical Grade chemical serves as a potent chelating agent that prevents scale formation and corrosion. Its ability to inhibit carbonate and sulfate scales makes it a cornerstone of modern water treatment.
Typical Properties
| Molecular formula | C2H8O7P2 |
|---|---|
| Molecular weight | 206.03 g/mol |
| Appearance | light beige powder |
| Form | Powder |
| Color | white |
| Melting point | 115-117 °C |
| Density | 1.45 (60% aq.) |
| Water solubility | Soluble in water. |
| pH | pH (1.7→100, 25°C) : 1.3～1.8 |
| GHS signal word | Danger · Corrosive, Irritant / harmful, Health hazard |
| HS code | 29319099 |
| Grades available | Technical Grade |
Typical literature values for identification; lot-specific results are stated on the certificate of analysis (COA) and the safety data sheet (SDS) that accompany every delivery.
Etidronic Acid
Applications
- Cooling Water Treatment: Prevents scale buildup in industrial cooling towers and heat exchangers.
- Detergent Formulation: Acts as a stabilizer for peroxide bleaching agents and a builder in heavy-duty cleaners.
- Metal Surface Treatment: Used as a cleaning agent for metals to remove oxides and prevent re-oxidation.
Safety & Risks
Classified as Corrosive to Metals and Serious Eye Damage Category 1. Proper PPE including chemical goggles and rubber gloves is required for safe handling.
Packaging
25 kg drums, 250 kg plastic drums, or 1250 kg IBC containers.