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1-Hydroxyethylidene-1,1-diphosphonic Acid (HEDP)


Synonyms: HEDP. HEDPA, 1-Hydroxyethylidene diphosphonic Acid; Etidronic acid; 1-Hydroxyethane-1,1-diphosphonic acid; Dequest 2010; Briquest ADPA-60AW; Unihib 106
CAS No.: 2809-21-4
EC No.: 220-552-8
Molecular Weight: 206.03
Molecular Formula: C2H8O7P2
Structural Formula: 1-Hydroxyethylidene-1,1-diphosphonic Acid (HEDP)


By reaction between glacial acetic acid and phosphorus trichloride, HEDP can be obtained: CH3COOH+2PCl3+5H2O→C2H8O7P2+6HCl. By product hydrogen chloride gas can also be applied in manufacturing Acetyl chloride which is raw material of herbicides and pharmaceuticals


By chelating with most earth metal ions such as Ca2+, Mg2+, Ba2+, and Fe2+, Pb2+, HEDP is used as scale inhibitor, deflocculant, sequestrant, water stabilizer in circulating cool water system, oil field and low-pressure boilers in fields such as electric power, chemical industry, metallurgy, fertilizer, etc under condition of high temperature and high pH value. HEDP is also used as detergent for metal and nonmetal. In dyeing industry, HEDP is used as peroxide stabilizer and dye-fixing agent; In non-cyanide electroplating, HEDP is used as chelating agent. The dosage of 1–10 mg/L is preferred as scale inhibitor, 10–50 mg/L as corrosion inhibitor, and 1000–2000 mg/L as detergent. Usually, HEDP is used together with polycarboxylic acid. Partial neutralized HEDP (usually with caustic soda, or potassium hydroxide) is also available in the above application.


Items Specification
Appearance pale yellow transparent liquid
HEDP active Content 60±2%
Phosphorous Acid (as PO3) 2.0% max.
Iron (as Fe) 20ppm max.
pH Value (1% aqueous) 2.0 max.
Color, APHA 80 max.
Density( 20°C), g/cm3 1.44~1.47
Acetic Acid 1.0% max.

Standard Packaging

250 or 290kgs/200L plastic drums, 1450kg/IBC

200L drums for HEDP

Risks and Safety Information

HEDP is regulated by UN as hazardous substance.
Danger! Corrosive Liquid, Organic, N.O.S.
UN 3265, Class 8, PG III
For more information, please see MSDS

Warning, Corrosive Liquid

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