Sodium persulfate

Sodium persulfate is the inorganic compound with the formula Na₂S₂O₈. It is the sodium salt of peroxydisulfuric acid, H₂S₂O₈, an oxidizing agent. It is a white solid that dissolves in water. It is almost non-hygroscopic and has good shelf-life.

Sodium persulfate

Two sodium cations and one peroxodisulphate anion
Ball-and-stick model of the crystal structure
Sodium persulfate as a white powder
Names
Other names Sodium peroxodisulfate Sodium peroxodisulphate Sodium peroxydisulfate Sodium peroxydisulphate
Identifiers
CAS Number	7775-27-1 Y
3D model (JSmol)	Interactive image
ChEMBL	ChEMBL502764 Y
ChemSpider	56406 Y
ECHA InfoCard	100.028.993
EC Number	231-892-1
PubChem CID	62655
RTECS number	SE0525000
UNII	J49FYF16JE Y
UN number	1505
CompTox Dashboard (EPA)	DTXSID4029698
InChI InChI=1S/2Na.H2O8S2/c;;1-9(2,3)7-8-10(4,5)6/h;;(H,1,2,3)(H,4,5,6)/q2*+1;/p-2 Y Key: CHQMHPLRPQMAMX-UHFFFAOYSA-L Y InChI=1/2Na.H2O8S2/c;;1-9(2,3)7-8-10(4,5)6/h;;(H,1,2,3)(H,4,5,6)/q2*+1;/p-2 Key: CHQMHPLRPQMAMX-NUQVWONBAA
SMILES [Na+].[Na+].O=S(=O)([O-])OOS([O-])(=O)=O
Properties
Chemical formula	Na2S2O8
Molar mass	238.10 g/mol
Appearance	White powder
Density	2.601 g/cm3[1]
Melting point	180 °C (356 °F; 453 K) decomposes
Solubility in water	55.6 g/100 ml (20 °C)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H272, H302, H315, H317, H319, H334, H335, H371
Precautionary statements	P220, P261, P280, P305+P351+P338, P342+P311
NFPA 704 (fire diamond)	2 0 1 OX
Flash point	Non-flammable
Safety data sheet (SDS)	ICSC 1136
Related compounds
Other anions	Sodium dithionite Sodium sulfite Sodium sulfate
Other cations	Potassium persulfate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Production

The salt is prepared by the electrolytic oxidation of sodium bisulfate:

2 NaHSO₄ → Na₂S₂O₈ + H₂

Oxidation is conducted at a platinum anode.^[2] In this way about 165,000 tons were produced in 2005.^[3]

The standard redox potential of sodium persulfate into hydrogen sulfate is 2.1 V, which is higher than that of hydrogen peroxide (1.8 V) but lower than ozone (2.2 V).^[4] The sulfate radical formed in situ has a standard electrode potential of 2.7 V.

However, there are a few drawbacks in utilizing platinum anodes to produce the salts; the manufacturing process is inefficient due to oxygen evolution and the product could contain contaminants coming from platinum corrosion (mainly due to extremely oxidizing nature of the sulfate radical). Thus, boron-doped diamond electrodes have been proposed as alternatives to the conventional platinum electrodes.^[5]

Structure

The sodium and potassium salts adopt very similar structures in the solid state, according to X-ray crystallography. In the sodium salt, the O-O distance is 1.476 Å. The sulfate groups are tetrahedral, with three short S-O distances near 1.44 and one long S-O bond at 1.64 Å.^[1]

Applications

It is mainly used as a radical initiator for emulsion polymerization reactions for styrene based polymers such as acrylonitrile butadiene styrene.^[3] It is also applicable for accelerated curing of low formaldehyde adhesives.

Other uses

It is a bleach, both standalone (particularly in hair cosmetics) and as a detergent component. It is a replacement for ammonium persulfate in etching mixtures for zinc and printed circuit boards, and is used for pickling of copper and some other metals.^{[citation needed]}

It is also used as a soil conditioner and for soil and groundwater remediation^[5][6] and in manufacture of dyestuffs, modification of starch, bleach activator, desizing agent for oxidative desizing, etc.

Organic chemistry

Sodium persulfate is a specialized oxidizing agent in chemistry, classically in the Elbs persulfate oxidation and the Boyland–Sims oxidation reactions. It is also used in radical reactions; for example in a synthesis of diapocynin from apocynin where iron(II) sulfate is the radical initiator.^[7]

Safety

The salt is an oxidizer and forms combustible mixtures with organic materials such as paper.