Potassium persulfate
 | |
 | |
 | |
| Names | |
|---|---|
| Other names
potassium peroxydisulfate Anthion potassium perdisulfate | |
| Identifiers | |
7727-21-1  | |
| 3D model (Jmol) | Interactive image |
| ChemSpider | 22821  |
| ECHA InfoCard | 100.028.893 |
| EC Number | 231-781-8 |
| E number | E922 (glazing agents, ...) |
| PubChem | 24412 |
| RTECS number | SE0400000 |
| UN number | 1492 |
| |
| |
| Properties | |
| K2S2O8 | |
| Molar mass | 270.322 g/mol |
| Appearance | white powder |
| Odor | odorless |
| Density | 2.477 g/cm3[1] |
| Melting point | < 100 °C (212 °F; 373 K) (decomposes) |
| 1.75 g/100 mL (0 °C) 4.49 g/100 ml (20 °C) | |
| Solubility | insoluble in alcohol |
| Refractive index (nD) |
1.467 |
| Structure | |
| triclinic | |
| Hazards | |
| Safety data sheet | ICSC 1133 |
| EU classification (DSD) |
Oxidant (O) Harmful (Xn) Irritant (Xi) |
| R-phrases | R8, R22, R36/37/38, R42/43 |
| S-phrases | (S2), S22, S24, S26, S37 |
| NFPA 704 | |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
| LD50 (median dose) |
802 mg/kg (oral, rat)[2] |
| Related compounds | |
| Other anions |
Potassium sulfite Potassium sulfate Potassium peroxymonosulfate |
| Other cations |
Sodium persulfate |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| verify (what is ?) | |
| Infobox references | |
- Not to be confused with potassium peroxymonosulfate.
Potassium persulfate is the inorganic compound with the formula K2S2O8. Also known as potassium peroxydisulfate or KPS, it is a white solid that is highly soluble in water. This salt is a powerful oxidant, commonly used to initiate polymerizations.
Preparation
Potassium persulfate can be prepared by electrolysis of a cold solution potassium bisulfate in sulfuric acid at a high current density.[1]
- 2 KHSO4 → K2S2O8 + H2
It can also be prepared by adding potassium bisulfate (KHSO4) to a solution of the more soluble salt ammonium peroxydisulfate (NH4)2S2O8. In principle it can be prepared by chemical oxidation of potassium sulfate using fluorine.
Uses
This salt is used to initiate polymerziation of various alkenes leading to commercially important polymers such as styrene-butadiene rubber and polytetrafluoroethylene and related materials. In solution, the dianion dissociates to give radicals:[3]
- [O3SO-OSO3]2− ⇌ 2 [SO4]−
It is used in organic chemistry as an oxidizing agent,[4] for instance in the Elbs persulfate oxidation of phenols and the Boyland–Sims oxidation of anilines.
As a strong yet stable bleaching agent it also finds use in various hair bleaches and lighteners. Such brief and non-continuous use is normally hazard free, however prolonged contact can cause skin irritation.[5] It has been used as an improving agent for flour with the E number E922, although it is no longer approved for this use within the EU.
Precautions
The salt is a strong oxidant and is incompatible with organic compounds. Prolonged skin contact can result in irritation.[5]
References
- 1 2 Brauer, Georg (1963). Handbook of Preparative Inorganic Chemistry Vol. 1, 2nd Ed. Newyork: Academic Press. p. 392. ISBN 978-0121266011.
- ↑ http://chem.sis.nlm.nih.gov/chemidplus/rn/7727-21-1
- ↑ Harald Jakob, Stefan Leininger, Thomas Lehmann, Sylvia Jacobi, Sven Gutewort (2005), "Peroxo Compounds, Inorganic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a19_177.pub2
- ↑ Encyclopedia of Reagents for Organic Synthesis, vol. 1, pp 193-197(1995)
- 1 2 "Final Report on the Safety Assessment of Ammonium, Potassium, and Sodium Persulfate". International Journal of Toxicology. 20 (3): 7-21. January 2001. doi:10.1080/10915810152630710.