CAS No.  29329-71-3 (x-Na), 3794-83-0 (4-Na)    Synonyms: Tetrasodium etidronate
Molecular Formula:C₂H₄O₇P₂Na₄                     Molecular weight: 294
Structural Formula:

Properties:
HEDP•Na4 is the sodium salt of HEDP, HEDP•Na4 is an good scale inhibitor for calcium carbonate, it can be used in low pressure boiler water system, circulating water system, industrial and municipal cleaning water system and swimming pool.
The solid HEDP•Na4 is white powder, soluble in water, easily deliquescence, suitable for use in winter and freezing districts. It is a kind of organophorphonic acid scale and corrosion inhibitor, can form stable complex with Fe, Cu and Zn ions, it can dissolve the oxides on metal surface, it has good scale and corrosion inhibition effect under 250℃.
HEDP•Na4 is widely used in circulating cool water system, medium and low pressure boiler, oil field water pipelines as scale and corrosion inhibitor in fields such as electric power, chemical industry, metallurgy, fertilizer, etc.. In light woven industry, HEDP•Na4 is used as detergent for metal and nonmetal. In dyeing industry, HEDP•Na4 is used as peroxide stabilizer and dye-fixing agent; In non-cyanide electroplating, HEDP•Na4 is used as chelating agent. 
Specification:

Items	Index
Appearance	Colorless to yellowish transparent liquid	White powder
Active content (HEDP)%	20.3-21.7	60.0 min
Active content (HEDP•Na4)%	29.0-31.0	85.0 min
Total phosphoric acid (as PO43-)%	18.4-20.4	55.0 min
Fe, mg/L	20.0 max	35.0 max
Moisture，%	--	9.0 max
Density (20℃)g/cm3	1.26-1.36	--
PH (1% water solution)	10.0-12.0	11.0-12.0

Package and Storage:
Liquid: 200L plastic drum, IBC(1000L), customers' requirement.
Solid: 25kg/bag, customers' requirement. Storage for ten months in shady room and dry place.
Safety Protection:
Weak acidity, Avoid contact with eye and skin, once contacted, flush with water.　
Synonyms:
Tetrasodium (1-hydroxyethylidene)bisphosphonate