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Percentage (%) concentration of FSO₂ forms (SO₂, HSO₃^-,& SO₃⁼) at different pH values

• When sulphur dioxide is added to juice or wine, the portion that exists as FSO₂ will be converted to the different forms of FSO₂ as shown by the equation and graph.
  
  
• Their concentrations are determined by the relevant disassociation constants and the pH of the juice or wine. (see graph and calculations)
  
  
• As the dissociation constant is constant at a given temperature, it is the pH that will determine the percentage of FSO₂ forms and hence pH is an important aspect of wine production.