
Peroxydisulfuric acid

Peroxydisulfuric acid is an inorganic compound with a chemical formula H2S2O8. Also called Marshall's acid after its inventor Professor Hugh Marshall, it is a sulfur oxoacid. In structural terms it can be written HO3SOOSO3H. It contains sulfur in its +6 oxidation state and a peroxide group. Its salts, commonly known as persulfates, are industrially important as powerful oxidizing agents.
Synthesis.
The acid is prepared by the reaction of chlorosulfuric acid with hydrogen peroxide:
Another method is the electrolysis of moderately concentrated sulfuric acid (60-70%) with platinum electrodes at high current density and voltage:
The basicity of this acid is 2.