Structure1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP)
CAS No. 2809-21-4
EC No. 220-552-8
Synonyms 1-Hydroxyethane-1,1-diphosphonic acid; 1-Hydroxyethylidene-1,1-diphosphonic acid; 1-hydroxyethylidenedi(phosphonic acid); Etidronic Acid; 1-Hydroxyethylidene-1,1-bis-(phosphonic acid); Ethane-1-hydroxy-1,1-diphosphonic acid; 1-Hydroxy-1,1-diphosphonoethane; Oxyethylidenediphosphonic acid

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

1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) acid with its CAS number 2809-21-4​  is a cost effective scale inhibitor used in various industrial applications such as industrial water treatment and detergents.

Additionally 1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP) shows a good stability in presence of chlorine as well as corrosion inhibition properties in presence of zinc and other phosphates and can also be used as chelating agent in the textile industry.


  • Cooling water systems / industrial water treatment
  • Industrial detergents
  • Swimming pools
  • Metal surface treatment as a corrosion inhibitor for steel
  • Stabilizer in H2O2 solutions
  • Sequestering agent in textile auxiliaries


Shelf Life

Under proper storage conditions, the shelf life is 12 months

Health & Safety

Detailed information on the product described can be found in our relevant Health and Safety Information (Material Safety Data Sheet)