DISODIUM ETIDRONATE- ▸ Chelation: Sequestrant for calcium, iron, and heavy-metal ions
- ▸ Scale control: Scale inhibitor in cooling and boiler water
- ▸ Corrosion inhibition: Metal-protection additive in water systems
- ▸ Detergents: Builder and stabilizer in cleaning formulations
A grade-specific Safety Data Sheet (SDS) — with the complete hazard classification, handling precautions, and transport information — is supplied with every shipment and available on request. Confirm all safety and regulatory details against the SDS for your specific grade.
Request SDS →Etidronic acid disodium salt — HEDP·Na2, the partially neutralized disodium salt of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), CAS 7414-83-7 (PubChem) — is an organophosphonate sequestrant. It binds calcium, iron, copper and other metal ions and inhibits scale and corrosion at sub-stoichiometric (threshold) doses, which makes it a core chelating and scale-control chemistry in cooling- and boiler-water treatment, detergents and industrial cleaning, oilfield and mining systems, and peroxide-bleach stabilization. The disodium salt is supplied for systems that benefit from a higher solution pH and easier handling than the free acid.
What is HEDP disodium salt?
HEDP is a phosphonate — a carbon-bonded analogue of polyphosphates that resists hydrolysis far better, so it keeps working in hot, high-hardness water where polyphosphates revert. Its multiple phosphonic-acid groups chelate hardness and transition-metal ions and adsorb onto the growing faces of scale crystals, distorting them so they cannot build adherent deposits even when the phosphonate is present at only a few ppm (the threshold effect). The disodium salt (HEDP·Na2) is the free acid neutralized to a moderate pH, dosed where lower acidity and simpler handling are preferred.
Applications by sector
Water treatment. HEDP·Na2 is a threshold scale inhibitor and sequestrant for calcium carbonate and calcium sulfate scale and a corrosion inhibitor in recirculating cooling water, boilers and reverse-osmosis systems, often combined with other phosphonates, polymers or zinc. Detergents and industrial cleaning. It is a chelant and builder that sequesters hardness, stabilizes the wash and protects surfaces. Oilfield and mining. It is used for scale control in produced-water and process streams. Pulp, paper and textile bleaching. It chelates the trace metals that catalyze peroxide decomposition, stabilizing hydrogen-peroxide bleach. HEDP is a sequestrant and scale inhibitor, not a registered biocide, and no disinfection or antimicrobial efficacy is claimed for it here.
HEDP acid vs disodium salt
The free acid (HEDP, CAS 2809-21-4) is the low-pH, highest-active form; the disodium salt (HEDP·Na2, CAS 7414-83-7) is partially neutralized for a higher solution pH and easier handling. The chelation and scale-inhibition chemistry is the same — choose the form that fits your dosing pH and materials of construction. RawSource can quote either; specify acid or salt, and the active concentration, on the RFQ.
Forms, grades and dosing
HEDP·Na2 is typically supplied as an aqueous solution at a stated active concentration (a dry grade is also available); confirm the active content against the CoA. Treatment dose depends on water chemistry, temperature, cycles of concentration and the rest of the program, so dose to your system and verify by residual testing rather than to a fixed percentage.
Handling and documentation
Each lot ships with a Certificate of Analysis (CoA) confirming identity and active content. Request the Safety Data Sheet (SDS) and technical data sheet for pH, density, concentration and handling guidance, which are sourced from those documents rather than reproduced here.
Bulk supply and RFQ
RawSource supplies HEDP disodium salt in bulk — drums, totes and IBCs — to water-treatment, detergent, oilfield and industrial-cleaning manufacturers, with CoA and SDS per lot. Submit an RFQ with your target quantity, active concentration and ship-to for a current quote. Related scale-control and chelation chemistries are covered in our scale inhibitors and antiscalants guide and the water treatment chemicals guide.
Typical Properties
Typical reference values, not a specification; the Certificate of Analysis (CoA) for the lot governs.
| Property | Typical Value |
|---|---|
| Chemical Name | Etidronic acid disodium salt (1-hydroxyethylidene-1,1-diphosphonic acid, disodium salt) |
| Synonyms | HEDP·Na2; disodium etidronate; HEDP disodium |
| CAS Number | 7414-83-7 |
| Molecular Formula | C2H6Na2O7P2 |
| Appearance | Typically a colorless to pale-yellow aqueous solution (dry grade also available) |
| Active content | Grade-dependent — see CoA |
| Solubility | Soluble in water |
| pH / density / concentration | Refer to the current SDS / technical data sheet |
| Function | Sequestrant, threshold scale inhibitor, corrosion inhibitor |
Regulatory & registration requirements
- TSCA (US):
- REACH (EU): Not determined from public registry
- EC number: 231-025-7
Source: EPA TSCA Inventory (July 2025 release) · ECHA CHEM — retrieved 2026-07-12
Frequently Asked Questions
What is HEDP disodium salt used for?
HEDP disodium salt (HEDP·Na2, CAS 7414-83-7) is an organophosphonate sequestrant used as a chelating agent, threshold scale inhibitor and corrosion inhibitor in cooling- and boiler-water treatment, detergents and industrial cleaning, oilfield and mining scale control, and as a peroxide-bleach stabilizer in pulp, paper and textiles.
Is HEDP disodium salt soluble in water?
Yes, HEDP disodium salt is water-soluble, which supports its use as an aqueous sequestrant and threshold scale inhibitor. See the SDS and technical data sheet for concentration and use-level guidance.
What is the formula and CAS of HEDP disodium salt?
It is the disodium salt of 1-hydroxyethylidene-1,1-diphosphonic acid, CAS 7414-83-7 (PubChem CID 23894), molecular formula C2H6Na2O7P2. The CoA confirms identity and active content for each lot.
What is the difference between HEDP and HEDP disodium salt?
HEDP is the free acid (CAS 2809-21-4); the disodium salt (HEDP·Na2, CAS 7414-83-7) is the partially neutralized form, supplied for applications that benefit from a higher solution pH and easier handling. The chelation and scale-inhibition chemistry is the same; specify acid or salt on the RFQ.
Is HEDP a biocide?
No. HEDP and its disodium salt are sequestrants and scale/corrosion inhibitors, not registered biocides; no disinfection or antimicrobial efficacy is claimed. In water-treatment programs biocidal control is provided by separate, registered products.
What is the price of HEDP disodium salt in bulk?
Bulk pricing depends on active concentration, packaging, order volume and freight, so RawSource quotes per order. Submit an RFQ with your target quantity and ship-to for a current bulk quote with CoA and SDS.
What is the REACH and TSCA regulatory status of Etidronic Acid Disodium Salt (HEDP.Na2)?
Etidronic Acid Disodium Salt (HEDP.Na2) (CAS 7414-83-7) is listed as Active on the U.S. EPA TSCA Inventory; its REACH registration status is not determined from the public ECHA registry.