Sulfuric acid has the formula of H 2 SO 4 . Sulfuric acid is the most important sulfur compound and one of the largest volume industrial chemicals. To produce it by the method known as contact process or solvay process, sulfur is first burned in air to yield sulfur dioxide SO 2 . The subsequent oxidation of SO 2 , is slow reaction, therefore a catalytic surface made of platinum or vanadium pentoxide is required. Sulfur trioxide reacts with water to yield sulfuric acid, because the oxide reacts with water to yield sulfuric acid; because the direct reaction of SO 2 and water produces a mist of H 2 SO 4 that is difficult to condense, the final stage of production takes place in two steps, SO 2 is first dissolved in H 2 SO 4 to produce pyrosulfuric acid; H 2 SO 4 , then sulfuric acid is produced by subsequent dilution of H 2 S 2 O 2 with water: SO 2 + H 2 SO 4 → H 2 S2O 2 H 2 S 2 O 2 + H 2 O → 2 H 2 SO 4 Pure sulfuric acid , a colorless oily liquid, is an extremely powerful