Trisodium phosphate

Trisodium phosphate
General
Systematic name	Trisodium phosphate dodecahydrate
Other names	Sodium phosphate tribasic
Molecular formula	Na3PO4·12H2O
Molar mass	380.1243 g/mol
Appearance	white crystalline solid
CAS number	[10101-89-0] (12H2O) [7601-54-9] (anhydr.)
EINECS number	231-509-8
Properties
Density and phase	1.620 g/cm³, solid
Solubility in water	1.5 g/100 ml (0 °C)
Melting point	73.5 °C decomp.
Basicity (pKb)	2.23
Structure
Coordination geometry	?
Crystal structure	Trigonal
Thermodynamic data
Standard enthalpy of formation ΔfH°solid	? kJ/mol
Standard molar entropy S°solid	? J.K−1.mol−1
Safety data
EU classification	not listed
PEL-TWA (OSHA)	–
Flash point	non flammable
RTECS number	TC9575000
Supplementary data page
Structure and properties	n, εr, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Sodium arsenate Sodium antimonate Sodium bismuthate
Other cations	Trilithium phosphate Tripotassium phosphate
Related compounds	Sodium dihydrogen phosphate Disodium hydrogen phosphate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Trisodium phosphate (TSP), available at most hardware stores in white powder form, is a cleaning agent and degreaser, commonly used to prepare household surfaces for painting. It can also be called trisodium orthophosphate and has the chemical formula Na₃PO₄. It is a highly water-soluble ionic salt. Solutions of it dissolved in water have an alkaline pH.

It can also be found as a food additive, under E number E339; it is used as an acidity regulator (buffering agent), emulsifier, thickening agent, nutrition enlargement agent and sequestrant (metal-chelating agent). In these uses it may be known as simply sodium phosphate. It also goes by this name when sold as an enema, working as a laxative to treat constipation. Sodium phosphate enemas are sold over-the-counter in the United States. However, it should not be confused with the related compounds sodium dihydrogen phosphate, also known as monosodium phosphate or MSP, and disodium hydrogen phosphate.

TSP for cleaning

Similar chemicals were once common in laundry and dishwashing detergents, but the phosphate, being a fertilizer, would cause algal blooms in the bodies of water that the drains led to. In the early 1970s the use of phosphate-containing products was limited. Now products sold as TSP Substitute, containing 80–90% sodium carbonate, are promoted as a direct substitute.

Cleaning products labeled as TSP may contain other ingredients as well, and may in fact be less than half TSP. So even "regular" TSP found at the hardware store may be half TSP and half "TSP substitute". Savogran's brand actually contains 80% trisodium phosphate dodecahydrate.

Although it is the active ingredient in at least one toilet bowl cleaning tablet, TSP is generally not good for cleaning bathrooms, because it can corrode metal.

TSP is commonly used after cleaning with mineral spirits in order to then clean up all the mineral spirits. TSP may be used with household chlorine bleach in the same solution, and this is particularly good for removing mildew from wood. The TSP alone can cause dark stains on redwood, and bleach prevents it.

Also used in various forms as a boiler treatment chemical for calcium precipitation, as well as regulating the caustic effects of disodium phosphate in coordinated phosphate chemistry.

External links

• TSP... CLEANING FOR THE BIG DOGS!!
• Safety data from IPCS INCHEM
• PubChem Substance Summary
• National Multiple Sclerosis Society's page on Sodium Phosphate enemas
• International Chemical Safety Card 1178