Ammonium persulfate (APS) is an inorganic compound with the chemical formula (NH4)2S2O8. It is a white salt that is highly soluble in water and is a strong oxidizing agent. It is used as a catalyst in polymer chemistry, as an etchant, and as a cleaning and bleaching agent.
Preparation and structure
Ammonium persulfate is prepared through electrolysis of a cold, concentrated solution of either ammonium sulfate or ammonium bisulfate in sulfuric acid using high current density. The ammonium, sodium, and potassium salts have similar structures in the solid state according to X-ray crystallography. In the ammonium salt, the O-O distance is 1.497 Å, and the sulfate groups are tetrahedral, with three short S-O distances near 1.44 Å and one long S-O bond at 1.64 Å.
Uses
As a source of radicals, APS is mainly used to initiate polymerization in certain alkenes. Important polymers produced using persulfates include styrene-butadiene rubber and polytetrafluoroethylene. In solution, the dianion dissociates into radicals. Its mechanism of action involves the sulfate radical adding to the alkene to produce a sulfate ester radical. It is also used along with tetramethylethylenediamine to catalyze the polymerization of acrylamide in making a polyacrylamide gel, making it important for SDS-PAGE and western blotting.
Ammonium persulfate’s powerful oxidizing properties make it useful for etching copper on printed circuit boards, as well as being a standard ingredient in hair bleach. It is also used as an oxidant in organic chemistry.
Safety
Ammonium persulfate is considered a potential irritant to the eyes, nose, throat, lung, and skin if it is inhaled as airborne dust. High levels of dust exposure may cause difficulty in breathing. Persulfate salts are a known cause of asthma, and exposure to ammonium persulfate has been linked to asthma in hair dressers and receptionists working in the hair care industry. This may be due to the oxidation of cysteine and methionine residues.