Peroxydisulfuric acid is an
inorganic compound with a
chemical formula
In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbol ...
. Also called Marshall's acid after Professor
Hugh Marshall
Hugh Marshall FRS FRSE FCS (7 January 1868 – 5 September 1913) was a Scottish chemist who discovered persulphates in 1891. He was the inventor of Marshall's acid. In 1902 he proposed the modified sign of equality which became standard in c ...
, who discovered it in 1891.
Structure and bonding
This
oxoacid
An oxyacid, oxoacid, or ternary acid is an acid that contains oxygen. Specifically, it is a compound that contains hydrogen, oxygen, and at least one other element, with at least one hydrogen atom bonded to oxygen that can dissociate to produce ...
features sulfur in its +6
oxidation state and a
peroxide group. Sulfur adopts the usual tetrahedral geometry.
Synthesis
The acid is prepared by the reaction of
chlorosulfuric acid with
hydrogen peroxide
Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%â ...
:
:2ClSO
3H + H
2O
2 → H
2S
2O
8 + 2 HCl
Another method is the electrolysis of moderately concentrated sulfuric acid (60-70%) with platinum electrodes at high current density and voltage:
:H
2SO
4 + H
2O → H
3O
+ + HSO
4− (dissociation of sulfuric acid)
:2HSO
4− → H
2S
2O
8 + 2e
− (E
0 = +2.4V) (bisulfate oxidation)
:2H
2SO
4 → H
2S
2O
8 + H
2 (overall reaction)
:3H
2O → O
3 + 6H
+ (ozone produced as a side product)
Uses
Peroxydisulfuric acid is a precursor to several salts including sodium peroxydisulfate, potassium peroxydisulfate, and ammonium peroxydisulfate. These salts are used to initiate the polymerization of
acrylonitrile
Acrylonitrile is an organic compound with the formula and the structure . It is a colorless, volatile liquid although commercial samples can be yellow due to impurities. It has a pungent odor of garlic or onions. In terms of its molecula ...
,
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 ...
, and related monomers. This application exploits the tendency of the peroxydisulfate anion to undergo homolysis to produce radicals. They are also used as cleaning of circuit boards.
[
]
See also
* Peroxymonosulfuric acid (Caro's acid)
* Piranha solution
Piranha solution, also known as piranha etch, is a mixture of sulfuric acid () and hydrogen peroxide (), used to clean organic compound, organic residues off substrates. Because the mixture is a strong oxidizing agent, it will decompose most orga ...
References
Hydrogen compounds
Peroxy acids
Persulfates
Sulfur oxoacids
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