Na3PO4

Trisodium phosphate, with the chemical formula Na3PO4, is an inorganic compound. It is the sodium salt of phosphoric acid. In its anhydrous form, it is a white, granular or crystalline solid. It is highly soluble in water, forming a strongly alkaline solution. This alkalinity is due to the hydrolysis of the phosphate ion, which reacts with water to produce hydroxide ions.

Trisodium phosphate is produced industrially by the reaction of phosphoric acid with sodium hydroxide or sodium carbonate. It has a variety of applications, although its use has been restricted in some areas due to environmental concerns related to eutrophication. Historically, it was widely used as a cleaning agent, food additive, and stain remover. In cleaning products, its effectiveness stems from its ability to emulsify grease and oil, suspend dirt particles, and soften water. As a food additive, it can act as a buffering agent, emulsifier, and nutrient supplement. It is often denoted by the E number E339(iii) in Europe when used as a food additive.

Despite its utility, the discharge of trisodium phosphate into waterways can contribute to eutrophication, a process where excessive nutrients lead to algal blooms and oxygen depletion, harming aquatic ecosystems. Consequently, many detergents and cleaning products no longer contain trisodium phosphate, or its use is regulated. In laboratory settings, it can be used as a buffer in biochemical experiments.