... with a complete phosphorous chemical industrial, from yellow phosphorus. 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid (HEDP)CAS No.: 2809-21-4Molecular Formula ... 0-62.089.0 minPhosphorous acid (as PO33-)%1.0 max0.5 maxPhosphoric acid (asPO43- )%0.5 max0.5 maxChloride (as Cl-)%0.3 max0.1 maxpH (1 ... , HEDP is used as chelating agent. The dosage of 1-10mg/L is preferred as scale inhibitor, 10-50mg/L ...