2(PtO2•4H2O) + H2C2O4 + 4H2SO4 → 2{H[Pt(SO4)2]•5H2O} + 2CO2 + 2H2O
Platinum(IV) oxide tetrahydrate react with oxalic acid and sulfuric acid to produce hydrogen disulfatoplatinate(III) pentahydrate, carbon dioxide and water. Sulfuric acid - concentrated solution.