Trisodium phosphate

Trisodium phosphate (TSP) is the inorganic compound with the chemical formula Na₃PO₄. It is a white, granular or crystalline solid, highly soluble in water producing an alkaline solution. TSPs are used as cleaning agent, lubricant, food additive, stain remover and degreaser.

The item of commerce is often partially hydrated and may range from anhydrous Na₃PO₄, to the dodecahydrate, Na₃PO₄·12 H₂O. Most often found in white powder form, it can also be called trisodium orthophosphate or simply sodium phosphate.

Production

Trisodium phosphate is produced by neutralization of phosphoric acid using sodium hydroxides, often with sodium carbonate. Carbonate can only produce disodium phosphate:

Uses

Cleaning

Trisodium phosphate was at one time extensively used in formulations for a variety of consumer grade soaps and detergents, and the most common use for trisodium phosphate has been in cleaning agents. The pH of a 1% solution is 12 (i.e., very basic), and the solution is sufficiently alkaline to saponify grease and oils. In combination with surfactants, TSP is an excellent agent for cleaning everything from laundry to concrete driveways. This versatility and low manufacturing price made TSP the basis for a plethora of cleaning products sold in the mid-20th century. TSP is still sold and used as a cleaning agent but since the late 1960s its use has diminished in the United States and many other parts of the world because, like many phosphate-based cleaners, it is known to cause extensive eutrophication of lakes and rivers once it enters a water system. Substitutes are generally not as effective.