H₂SO₄ is a very stable oxyacid of sulfur. It is often called king of chemicals, since it is one of the most useful chemicals in industry.

Manufacture of sulfuric acid : H₂SO₄ can be manufactured by following process,

Lead chamber process: In this process, SO₂ is oxidized to SO₃ by the oxides of nitrogen and the SO₃ thus formed is dissolved in steam to form H₂SO₄.

SO₂ + NO₂ —> SO₃ + NO ; 2NO + O₂ —> 2NO₂

SO₃ + H₂O —> H₂SO₄

Contact process: In the contact process, SO₂ obtained by burning of S or iron pyrities is catalytically oxidized to SO₃ in presence of finely divided Pt or V₂O₅ as catalyst.

S + O₂ SO₂ or 4FeS₂ + 11O₂ —> 2Fe₂O₃ + 8SO₂

2SO₂ + O₂ 2SO₃.

V₂O₅ is, however, preferred since is much cheaper than Pt and is also not poisoned by arsenic impurities.

The favorable conditions for maximum yield of SO₃ are,

(a) High concentration of SO₂ and O_2. (b) Low temperature of 673 to 723 K, (c) High pressure about 2 atmospheres.

SO₃ thus obtained is absorbed in 98% H₂SO₄ to form oleum which on dilution with water gives H₂SO₄ of desired concentration.

Contact process is preferred over lead chamber process (gives 98% pure H₂SO₄) since it gives H₂SO₄ of greater purity (100%).