Description

Sodium Tripolyphosphate (STPP) — also known as sodium triphosphate — is an inorganic compound with the chemical formula Na₅P₃O₁₀. It is a white, crystalline or granular powder that is highly soluble in water. STPP consists of three phosphate units linked together, forming a triphosphate anion (P₃O₁₀⁵⁻), which can bind to multiple cations like calcium and magnesium. This chelating ability gives it many of its useful properties.

Chemical Properties

Formula: Na₅P₃O₁₀

Molecular Weight: 367.86 g/mol

Appearance: White powder or granules

Solubility: Soluble in water, insoluble in organic solvents

pH (1% solution): Typically 9–10

Health and Environmental Considerations

Generally recognized as safe (GRAS) in regulated food amounts.

Overuse in detergents can contribute to eutrophication — excessive nutrient enrichment of water bodies that leads to algal blooms.

Handling requires care, as it can cause irritation to eyes and skin.