Na5P3O10

Na5P3O10, commonly known as sodium tripolyphosphate (STPP), is the sodium salt of triphosphoric acid with the empirical formula Na5P3O10. It is a linear polyphosphate consisting of three phosphate units linked by P–O–P bridges. In its solid form, it appears as a white crystalline powder that is highly soluble in water.

Production and structure: STPP is produced by high-temperature condensation of phosphoric acid with sodium-bearing bases, typically followed by neutralization and purification. The material represents a member of the polyphosphate family, with Na5P3O10 describing the tripolyphosphate chain. In aqueous solutions, it can hydrolyze to shorter polyphosphates and orthophosphate species depending on pH and temperature.

Properties: The compound has a molar mass of about 367.86 g/mol. It is stable under neutral to alkaline conditions and is readily soluble in water. STPP acts as a sequestering agent for multivalent cations and serves as a buffering component in certain formulations. It can degrade over time or under acidic or high-temperature conditions.

Applications: In detergents and cleaners, STPP functions as a water-softening builder by binding calcium and magnesium ions, enhancing surfactant performance. In food processing, it is used as a buffering agent, emulsifier, and moisture-retaining additive in meats, seafood, and prepared products, within regulatory limits. It is also employed in textiles and paper processing to control pH and improve processing characteristics.

Regulation and environment: Phosphates used in household detergents are restricted in many regions due to concerns about eutrophication. Food-grade STPP is subject to food additive regulations that vary by country. Manufacturing, usage, and disposal are governed by environmental and safety guidelines to manage potential ecological and health impacts.