Sodium persulfate is the inorganic compound with the formula Na₂ S₂ O₈. It is the sodium salt of

peroxydisulfuric acid Peroxydisulfuric acid is an inorganic compound with a chemical formula . Also called Marshall's acid after Professor Hugh Marshall, who discovered it in 1891. Structure and bonding This oxoacid features sulfur in its +6 oxidation state and a ...

, H₂S₂O₈, an

oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...

. It is a white solid that dissolves in water. It is almost non-

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substan ...

and has good shelf-life.

Production

The salt is prepared by the electrolytic oxidation of

sodium bisulfate Sodium bisulfate, also known as sodium hydrogen sulfate, is the sodium salt of the bisulfate anion, with the molecular formula NaHSO4. Sodium bisulfate is an acid salt formed by partial neutralization of sulfuric acid by an equivalent of sodium ...

: :2 NaHSO₄ → Na₂S₂O₈ + H₂ Oxidation is conducted at a platinum anode. In this way about 165,000 tons were produced in 2005. 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). The sulfate radical formed in situ has a

standard electrode potential In electrochemistry, standard electrode potential E^\ominus, or E^\ominus_, is a measure of the reducing power of any element or compound. The IUPAC "Gold Book" defines it as: ''"the value of the standard emf (electromotive force) of a cell in wh ...

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.

Structure

The sodium and potassium salts adopt very similar structures in the solid state, according to

X-ray crystallography X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

. In the sodium salt, the O-O distance is 1.476Å. The sulfate groups are tetrahedral, with three short S-O distances near 1.44 and one long S-O bond at 1.64Å.

Applications

It is mainly used as a

radical initiator In chemistry, radical initiators are substances that can produce radical species under mild conditions and promote radical reactions. These substances generally possess weak bonds—bonds that have small bond dissociation energies. Radical i ...

for

emulsion polymerization Emulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer ...

reactions for

styrene Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...

based polymers such as Acrylonitrile butadiene styrene. Also applicable for accelerated curing of low

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

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 Ammonium persulfate (APS) is the inorganic compound with the formula (NH4)2S2O8. It is a colourless (white) salt that is highly soluble in water, much more so than the related potassium salt. It is a strong oxidizing agent that is used as a catalys ...

etching Etching is traditionally the process of using strong acid or mordant to cut into the unprotected parts of a metal surface to create a design in intaglio (incised) in the metal. In modern manufacturing, other chemicals may be used on other types ...

mixtures for

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

and printed circuit boards, and is used for

pickling Pickling is the process of preserving or extending the shelf life of food by either anaerobic fermentation in brine or immersion in vinegar. The pickling procedure typically affects the food's texture and flavor. The resulting food is cal ...

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

and some other metals. It is also used as a soil conditioner and for soil and

groundwater remediation Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the sub ...

and in manufacture of dyestuffs, modification of starch, bleach activator, desizing agent for oxidative desizing, etc.

Organic chemistry

Sodium persulfate is a specialized

in chemistry, classically in the

Elbs persulfate oxidation The Elbs persulfate oxidation is the organic reaction of phenols with alkaline potassium persulfate to form ''para''-diphenols. The reaction is generally performed in water at room temperatures or below, using equimolar quantities of reagents. ...

and the

Boyland–Sims oxidation The Boyland–Sims oxidation is the chemical reaction of anilines with alkaline potassium persulfate, which after hydrolysis forms ''ortho''-hydroxyl anilines. The reaction is generally performed in water at room temperatures or below, using equim ...

reactions. It is also used in radical reactions; for example in a synthesis of diapocynin from apocynin where

iron(II) sulfate Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the heptahydrate (''x'' = 7) but several values for x are know ...

is the radical initiator. :

Safety

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

References

{{Sodium compounds Persulfates Sodium compounds Oxidizing agents