Ammonium Persulfate

Ammonium persulfate (NH₄)₂S₂O₈ is a white crystalline inorganic compound. It is a white powder-like salt and is highly soluble in water. It has the chemical formula (NH₄)₂S₂O₈.

Hugh Marshall prepared this compound for the first time.

Structure and Chemical Formula

Ammonium persulfate is an ionic compound with a +1 charge on the cation and a -2 charge on the anion. Its chemical formula is (NH₄)₂S₂O₈ and its structure is as follows.

The value of ammonium persulfate molar mass is 228.18 g/mol.

Physical Properties

Chemical Properties

1. The white crystalline compound decomposes in an aqueous medium to form ammonium ions and peroxydisulfate oxyanions. This further decomposes into sulfate ions. Therefore the decomposition of the compound can result in the formation of sulfuric acid fumes.

2. Oxidation of alkynes using ammonium persulfate and diphenyl diselenide as catalyst in aqueous media results in 1,2 dicarbonyl derivatives or hemiacetals (starting from terminal alkynes).

3. It is a strong and stable oxidising agent.

Production

Ammonium Persulfate can be produced via the electrolysis of ammonium sulfate (NH₄)₂SO₄ and sulfuric acid H₂SO₄ followed by crystallisation of the electrolytic solution.

The sulfuric acid is electrolysed to hydrogen sulfate ions HSO₄⁻ at the anode. 2 hydrogen sulfate ions form peroxydisulfate acid H₂S₂O₈, which reacts with the ammonium sulfate to form ammonium persulfate and sulfuric acid. 

H₂SO₄  ↔ H⁺ + HSO₄⁻

Anode Reaction:

2 HSO₄⁻ ─ 2e⁻ → H₂S₂O₈

Cathode Reaction: 

2 H⁺ + 2e⁻ → H₂ ↑

Reaction of Peroxydisulfate Acid with Ammonium Sulfate:

(NH₄)₂SO₄ + H₂S₂O₈ → (NH₄)₂S₂O₈ + H₂SO₄

The remaining solution is crystallised in order to extract the the required compound (NH₄)₂S₂O₈.

Applications of Ammonium Persulfate

Some of the several applications of this inorganic compound includes:

• Preservative in food products
• Ingredient in hair bleaches
• Used in PCBs (printed circuit boards)
• Used as a general oxidising agent
• Also used as an initiator in several polymerisation reactions.

Ammonium Persulfate Hazards

(NH₄)₂S₂O₈ is an irritant. Inhaling dust containing the compound can irritate the lungs, and in severe cases can also cause asthma. 

Coming in contact with this compound can irritate eyes and cause skin allergies. High exposure to the compound can lead to fluid build-up in the lungs or “pulmonary edema”, in which case immediate medical supervision is required.

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