Ammonium Persulfate (CAS: 7727-54-0)

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 in polymer chemistry, as an etchant, and as a cleaning andbleaching agent.

The dissolution of the salt in water is endothermic.

Preparation

Ammonium persulfate is prepared by electrolysis of a cold concentrated solution

ammonium sulfate in sulfuric acid at a high current density.[1] The method was

first described by H. Marshall.

Uses

As an oxidizer and a source of radicals, APS finds many commercial applications.

Salts of peroxydisulfate are mainly used as radical initiators in the polymerization of

certain alkenes. Commercially important polymers prepared using persulfates include

styrene-butadiene rubber and polytetrafluoroethylene. In solution, the dianion dissociates

to give radicals:

[O3SO-OSO3]2-   2 [SO4]-

The sulfate radical adds to the alkene to give a sulfate ester radical. It is also used along with

tetramethylethylenediamine to catalyze the polymerization of acrylamide in making a polyacrylamide gel.

Illustrative of its powerful oxidizing properties, it is used to etch copper on printed circuit boards

as an alternative to ferric chloride solution. This property was discovered many years ago. In 1908,

John William Turrentine used a dilute ammonium persulfate solution to etch copper. Turrentine

weighed copper spirals before placing the copper spirals into the ammonium persulfate solution for

an hour. After an hour, the spirals were weighed again and the amount of copper dissolved by ammonium

persulfate was recorded. This experiment was extended to other metals such as nickel, cadium, and iron,

all of which yielded similar results. The oxidation equation is thus: 1/2 S2O8 (aq)2- + e- -> SO4 (aq)2-.

Ammonium persulfate is the main component of Nochromix, a laboratory cleaning agent. On dissolving

in sulfuric acid, it is used to clean laboratory glassware as a metal-free alternative to chromic acid baths.

It is also a standard ingredient in western blot gels and hair bleach.

Persulfates are used as oxidants in organic chemistry.

Safety

Airborne dust may be irritating to eye, nose, throat, lung and skin upon contact. Exposure to

high levels of dust may cause difficulty in breathing.

It has been noted that persulfate salts are a major cause of asthmatic effects in women.[9]

Furthermore, it has been suggested that exposure to ammonium persulfate can cause asthmatic

effects in hair dressers and receptionists working in the hair dressing industry. These asthmatic

effects are proposed to be caused by the oxidation of cysteine residues, as well as methionine residues.