text: In the first step, sulfur is burned to produce sulfur dioxide:
  : (−297 kJ/mol)
  or, alternatively, hydrogen sulfide () gas is incinerated to  gas:
  : (−1036 kJ/mol)
  The sulfur dioxide then oxidized to sulfur trioxide using oxygen with vanadium(V) oxide as catalyst.
  : (−198 kJ/mol) (reaction is reversible)
  The sulfur trioxide is hydrated into sulfuric acid :
  : (−101 kJ/mol)
  The last step is the condensation of the sulfuric acid to liquid 97–98% :
  : (−69 kJ/mol)