Н2S-SO2-Na2SO3-SO2-SO3-K2SO4-BaSO4
2H₂S + 3O₂ = 2SO₂ + 2H₂O SO₂ + 2NaOH = Na₂SO₃ + H₂O Na₂SO₃ + 2HCl =2NaCl + SO₂ + H₂O 2SO₂ + O₂ = 2SO₃ SO₃ + 2KOH = K₂SO₄ + H₂O K₂SO₄ + Ba(NO₃)₂ = 2KNO₃ + BaSO₄