Polyphosphate

Polyphosphates are phosphate polymers linked between hydroxyl groups and hydrogen atoms. The polymerization that takes place is known as a condensation reaction. Phosphate bonds are typically high-energy and are difficult to separate. Adenosine triphosphate (ATP) is an example of a phosphate trimer, a polymer with three phosphate groups.

Sodium tri-polyphosphate (Na₅P₃O₁₀) has been used widely as a constituent of laundry detergents, acting as a water softener in hard water regions and improving detergent performance. In recent years, concern has grown that this results in substantial amounts of phosphates entering the sewage system and thence to watercourses, resulting in eutrophication. This has led to the amounts of polyphosphates in detergents being legally controlled in a number of countries (e.g., Germany, Italy, Austria)